ACP Holdings Acquisition Corp.

As filed with the Securities and Exchange Commission on March 6, 2026.

Registration No. 333-

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORMS-1

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

(Exact name of registrant as specified in its charter)

3131 Eastside, Houston, Texas 77098

Tel: 832-810-6648

(Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

Andrew Mallozzi

3131 Eastside, Houston, Texas 77098

Tel: 832-810-6648

(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copies to:

Approximate date of commencement of proposed sale to the public: As soon as practicable after the effective date of this registration statement.

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933 check the following box.☐

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.☐

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.☐

If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act.☐

The Registrant hereby amends this Registration Statement on such date or dates as may be necessary to delay its effective date until the Registrant shall file a further amendment which specifically states that this Registration Statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933, as amended, or until the Registration Statement shall become effective on such date as the Securities and Exchange Commission, acting pursuant to said Section 8(a), may determine.

The information in this prospectus is not complete and may be changed. We may not sell these securities until the registration statement filed with the Securities and Exchange Commission is effective. This prospectus is not an offer to sell these securities and it is not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not permitted.

$200,000,000

20,000,000 Units

ACP Holdings Acquisition Corp. is a blank check company incorporated as a Cayman Islands exempted company and formed for the purpose of effecting a merger, amalgamation, share exchange, asset acquisition, share purchase, reorganization or similar business combination with one or more businesses, which we refer to throughout this prospectus as our initial business combination. We have not selected any business combination target and we have not, nor has anyone on our behalf, initiated any substantive discussions, directly or indirectly, with any business combination target. We may pursue an initial business combination in any business or industry.

This is an initial public offering of our securities. Each unit has an offering price of $10.00 and consists of one Class A ordinary share and one-third of one redeemable warrant. Each whole warrant entitles the holder thereof to purchase one Class A ordinary share at a price of $11.50 per share, subject to adjustment as described herein. Only whole warrants are exercisable. No fractional warrants will be issued upon separation of the units and only whole warrants will trade. The warrants will become exercisable 30 days after the completion of our initial business combination and will expire five years after the completion of our initial business combination or earlier upon redemption or our liquidation, as described herein. The underwriters have a 45-day option from the date of this prospectus to purchase up to an additional 3,000,000 units to cover over-allotments, if any.

We are an “emerging growth company” under applicable federal securities laws and will be subject to reduced public company reporting requirements. No offer or invitation to subscribe for securities may be made to the public in the Cayman Islands.

We will provide our public shareholders with the opportunity to redeem, regardless of whether they abstain, vote for, or vote against, our initial business combination, all or a portion of their Class A ordinary shares that are sold as part of the units in this offering, which we refer to collectively as our public shares, upon the completion of our initial business combination at a per-share price, payable in cash, equal to the aggregate amount then on deposit in the trust account described below as of two business days prior to the consummation of our initial business combination, including interest earned on the funds held in the trust account, less taxes payable (excluding any U.S. federal excise tax on stock repurchases under the Inflation Reduction Act of 2022, or similar tax, that is imposed on us, if any), divided by the number of then outstanding public shares, subject to the limitations and on the conditions described herein. See “Summary — The Offering — Redemption rights for public shareholders upon completion of our initial business combination” and “Summary — The Offering — Redemption of public shares and distribution and liquidation if no initial business combination” for more information.

Notwithstanding the foregoing redemption rights, if we seek shareholder approval of our initial business combination and we do not conduct redemptions in connection with our initial business combination pursuant to the tender offer rules, our amended and restated memorandum and articles of association will provide that a public shareholder, together with any affiliate of such shareholder or any other person with whom such shareholder is acting in concert or as a “group” (as defined under Section 13 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), will be restricted from redeeming its shares with respect to more than an aggregate of 15% of the shares sold in this offering without our prior consent. However, we would not be restricting our shareholders’ ability to vote all of their shares (including all shares held by those shareholders that hold more than 15% of the shares sold in this offering) for or against our initial business combination. See “Summary — The Offering — Limitation on redemption rights of shareholders holding 15% or more of the shares sold in this offering if we hold shareholder vote” for further discussion on certain limitations on redemption rights.

Our sponsor, Union Street Sponsor, LLC, has committed to purchase an aggregate of 390,000 units, or “private placement units,” at a price of $10.00 per unit, or $3,900,000 in the aggregate, in a private placement that will close simultaneously with the closing of this offering. Each private placement unit will consist of one Class A ordinary share and one-third of one warrant, with each whole warrant exercisable to purchase one Class A ordinary share at $11.50 per share. We refer to the shares included in the private placement units throughout this prospectus as the “private placement shares” and the warrants included in the private placement units as the “private placement

warrants.” The private placement units are identical to the units sold in this offering, subject to certain limited exceptions as described in this prospectus. The private placement warrants will be identical to the warrants comprising part of the units being offered by this prospectus.

On January 29, 2026, our sponsor paid $25,000 to cover certain of our offering costs in exchange for 7,666,667 Class B ordinary shares, up to 1,000,000 of which will be surrendered to us for no consideration after the closing of this offering depending on the extent to which the underwriters’ over-allotment option is exercised, which will automatically convert into Class A ordinary shares immediately prior to, concurrently with, or immediately following the consummation of our initial business combination, or earlier at the option of the holders thereof on a one-for-one basis, subject to the adjustments described herein.

The number of founder shares outstanding was determined based on the expectation that the total size of this offering would be a maximum of 23,000,000 public units if the underwriters’ over-allotment option is exercised in full, and therefore that such founder shares would represent 25% of the outstanding shares after this offering (not including the Class A ordinary shares comprising part of the private placement units and the Class A ordinary shares underlying the private placement warrants). If we increase or decrease the size of the offering, we will effect a share capitalization or a share repurchase or redemption or other appropriate mechanism, as applicable, with respect to our Class B ordinary shares immediately prior to the consummation of the offering in such amount as to maintain the ownership of founder shares by our sponsor, on an as-converted basis, at 25% of our issued and outstanding ordinary shares upon the consummation of this offering (not including the Class A ordinary shares comprising part of the private placement units and the Class A ordinary shares underlying the private placement warrants). Further, the Class A ordinary shares issuable in connection with the conversion of the founder shares or an increase in the size of the offering may result in material dilution to our public shareholders due to the anti-dilution rights of our founder shares that may result in an issuance of Class A ordinary shares on a greater than one-to-one basis upon conversion. Prior to the closing of our initial business combination, only holders of our Class B ordinary shares (i) will have the right to vote to appoint and remove directors prior to or in connection with the completion of our initial business combination and (ii) will be entitled to vote on continuing our company in a jurisdiction outside the Cayman Islands (including any special resolution required to amend our constitutional documents or to adopt new constitutional documents, in each case, as a result of our approving a transfer by way of continuation in a jurisdiction outside the Cayman Islands). On any other matters submitted to a vote of our shareholders prior to or in connection with the completion of our initial business combination, holders of the Class B ordinary shares and holders of the Class A ordinary shares will vote together as a single class, except as required by law. See “Summary — The Offering — Sponsor Information” for further discussion on our sponsor’s and our affiliates’ securities and compensation.

As more fully discussed in “Management — Conflicts of Interest,” each of our officers and directors presently has, and any of them in the future may have additional, fiduciary, contractual or other obligations or duties to one or more other entities, pursuant to which such officer or director is or will be required to present a business combination opportunity to such entities. The low price that our sponsor, officers and directors (directly or indirectly) paid for the founder shares creates an incentive whereby our officers and directors could potentially make a substantial profit even if we select an acquisition target that subsequently declines in value and is unprofitable for public shareholders. If we are unable to complete our initial business combination within the completion window, or by such earlier liquidation date as our board of directors may approve, the founder shares and private placement units (and the securities comprising such units) may be worthless, except to the extent they receive liquidating distributions from assets outside the trust account, which could create an incentive for our sponsor, officers and directors to complete a transaction even if we select an acquisition target that subsequently declines in value and is unprofitable for public shareholders. Further, each of our officers and directors may have a conflict of interest with respect to evaluating a particular business combination if the retention or resignation of any such officers and directors was included by a target business as a condition to any agreement with respect to our initial business combination. Additionally, we will reimburse our sponsor or an affiliate of our sponsor in an amount equal to $25,000 per month for office space, utilities and secretarial and administrative services provided to members of our management team prior to the consummation of our initial business combination, as described elsewhere in this prospectus. $10,000 of that monthly fee will be paid in cash on a monthly basis, and $15,000 of that monthly fee will be accrued and payable only upon the consummation of our initial business combination. Upon consummation of this offering, we will repay up to $400,000 in loans made to us by Union Street Management Sponsor, LLC, an affiliate of our sponsor to cover offering-related and organizational expenses. In the event that following this offering we obtain working capital loans from our sponsor, officers or directors, or their respective affiliates, to finance transaction costs related to our initial business combination, up to $1,500,000 of such loans may be convertible into private placement

units of the post-business combination entity at a price of $10.00 per unit at the option of the lender. Prior to or in connection with the completion of our initial business combination, we may pay our sponsor, officers or directors, or their respective affiliates, a finder’s fee, advisory fee, consulting fee or success fee for any services they render to us in order to effectuate the completion of our initial business, which, if made prior to the completion of our initial business combination, will be paid from funds held outside the trust account. Upon consummation of our initial business combination, we will also reimburse our sponsor, officers or directors, or their respective affiliates for any out-of-pocket expenses related to identifying, investigating and completing an initial business combination. The founder shares and other securities to be received by our sponsor, officers and directors (including private placement shares comprising part of private placement units issued upon conversion of working capital loans) may result in a material dilution of the public investors’ equity interests. See “Risk Factors — Risks Relating to our Management Team — The nominal purchase price paid by our sponsor for the founder shares may result in significant dilution to the implied value of your public shares upon the consummation of our initial business combination, and our sponsor is likely to make a substantial profit on its investment in us in the event we consummate an initial business combination, even if the business combination causes the trading price of our ordinary shares to materially decline,” “Proposed Business — Effecting our initial business combination — Selection of a target business and structuring of our initial business combination,” “Management — Officers, Directors and Director Nominees” and “Certain Relationships and Related Party Transactions.”

We have until the date that is 24 months from the closing of this offering or until such earlier liquidation date as our board of directors may approve, to consummate our initial business combination. If we anticipate that we may be unable to consummate our initial business combination within such 24-month period, we may seek shareholder approval to amend our amended and restated memorandum and articles of association to extend the date by which we must consummate our initial business combination. Subject to shareholder approval, there are no limitations as to the duration of an extension or the number of times the completion window may be extended by shareholders via an amendment to our amended and restated memorandum and articles of association. If we seek shareholder approval for an extension, holders of public shares will be offered an opportunity to redeem their shares at a per share price, payable in cash, equal to the aggregate amount then on deposit in the trust account, including interest earned thereon (less taxes payable (excluding any U.S. federal excise tax on stock repurchases under the Inflation Reduction Act of 2022, or similar tax, that is imposed on us, if any)), divided by the number of then issued and outstanding public shares, subject to applicable law. If we are unable to complete our initial business combination within 24 months from the closing of this offering and do not hold a shareholder vote to amend our amended and restated memorandum and articles of association to extend the amount of time we will have to consummate an initial business combination, or by such earlier liquidation date as our board of directors may approve, we will redeem 100% of the public shares at a per share price, payable in cash, equal to the aggregate amount then on deposit in the trust account, including interest earned thereon (less taxes payable (excluding any U.S. federal excise tax on stock repurchases under the Inflation Reduction Act of 2022, or similar tax, that is imposed on us, if any) and up to $100,000 of interest income to pay dissolution expenses), divided by the number of then issued and outstanding public shares, subject to applicable law as further described herein.

Currently, there is no public market for our units, Class A ordinary shares or warrants. We intend to apply to have our units listed on The Nasdaq Global Market, or Nasdaq, under the symbol “ACGCU,” on or promptly after the date of this prospectus. We cannot guarantee that our securities will be approved for listing on Nasdaq. We expect the Class A ordinary shares and warrants comprising the units to begin separate trading on the 52 nd day following the date of this prospectus unless Roth Capital Partners, LLC the representative of the underwriters, informs us of its decision to allow earlier separate trading, subject to our satisfaction of certain conditions as described further herein. Once the securities comprising the units begin separate trading, we expect that the Class A ordinary shares and warrants will be listed on Nasdaq under the symbols “ACGC” and “ACGCW”, respectively.

We are an “emerging growth company” and a “smaller reporting company” under applicable federal securities laws and will be subject to reduced public company reporting requirements. Investing in our securities involves a high degree of risk. See “Risk Factors” beginning on page 46 for a discussion of information that should be considered in connection with an investment in our securities. Investors will not be entitled to protections normally afforded to investors in Rule 419 blank check offerings.

Neither the U.S. Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

No offer or invitation, whether directly or indirectly, is being or may be made to the public in the Cayman Islands to subscribe for any of our securities.

(1) Includes $0.10 per unit sold in this offering (excluding any units sold pursuant to the underwriters’ over-allotment option), or $2,000,000 in the aggregate, payable to the underwriters upon the closing and $0.10 per unit sold pursuant to the underwriters’ over-allotment option, or up to $300,000 in the aggregate if the underwriters’ over-allotment option is exercised in full, to be deposited in the trust account and released to the underwriters only upon the completion of an initial business combination. Also includes up to $0.20 per unit sold in this offering, or up to $4,000,000 in the aggregate (or up to $4,600,000 in the aggregate if the underwriters’ over-allotment option is exercised in full), payable to the underwriters for deferred underwriting commissions to be deposited in a trust account and released to the underwriters only upon the completion of an initial business combination. Such deferred underwriting commissions will be payable as follows: (i) $0.05 per unit sold in this offering, or $1,000,000 in the aggregate (or up to $1,150,000 in the aggregate if the underwriters’ over-allotment option is exercised in full); (ii) $0.05 per unit sold in this offering, or $1,000,000 in the aggregate (or up to $1,150,000 in the aggregate if the underwriters’ over-allotment option is exercised in full), payable only if, immediately prior to the consummation of our initial business combination, the funds remaining in the trust account equal or exceed 20% of the total gross proceeds of this offering, calculated based on the percentage of public shares outstanding immediately prior to the consummation of our initial business combination, net of public shares submitted for redemption and net of any public shares held by public shareholders that have entered into forward purchase agreements or other arrangements whereby we have a contractual obligation to repurchase such shares after the closing of the initial business combination and any required repurchases pursuant to forward purchase agreements or similar arrangements; and (iii) up to 1.0% of the funds remaining in the trust account, calculated based on the percentage of public shares outstanding immediately prior to the consummation of our initial business combination, net of public shares submitted for redemption and net of any public shares held by public shareholders that have entered into forward purchase agreements or other arrangements whereby we have a contractual obligation to repurchase such shares after the closing of the initial business combination. See also “Underwriting” for a description of compensation and other items of value payable to the underwriters.

Of the proceeds we receive from this offering and the sale of the private placement units described in this prospectus, $200.0 million, or $230.0 million if the underwriters’ over-allotment option is exercised in full ($10.00 per unit in either case), will be placed into a U.S.-based trust account with Odyssey Transfer and Trust Company acting as trustee.

Because our sponsor acquired the founder shares at a nominal price, our public shareholders will incur an immediate and substantial dilution upon the closing of this offering, assuming no value is ascribed to the warrants included in the units. Further, the Class A ordinary shares issuable in connection with the conversion of the founder shares or an increase in the size of the offering may result in material dilution to our public shareholders due to the anti-dilution rights of our founder shares that may result in an issuance of Class A ordinary shares on a greater than one-to-one basis upon conversion. See the section titled “Risk Factors — Risks Relating to our Management Team — The nominal purchase price paid by our sponsor for the founder shares may result in significant dilution to the implied value of your public shares upon the consummation of our initial business combination, and our sponsor is likely to make a substantial profit on its investment in us in the event we consummate an initial business combination, even if the business combination causes the trading price of our ordinary shares to materially decline.”In addition, the cashless exercise of the private placement warrants comprising part of the private placement units purchased by our sponsor at the closing of this offering would increase the dilution to our public shareholders. Further, the conversion of any working capital loans into placement units, as well as the cashless exercise of the private placement warrants that are issued as part of such units, would further increase the dilution to our public shareholders.

The following table illustrates the difference between the public offering price per unit and our net tangible book value per share (NTBV), as adjusted to give effect to this offering and assuming the redemption of our public shares at varying levels and the exercise in full and no exercise of the over-allotment option. See section entitled “Dilution” for more information.

Our sponsor, officers and directors will directly or indirectly own our securities following this offering, and accordingly, they may have a conflict of interest in determining whether a particular target business is an appropriate business with which to effectuate our initial business combination. Additionally, each of our officers and directors presently has, and any of them in the future may have additional, fiduciary, contractual or other obligations or duties to one or more other entities, pursuant to which such officer or director is or will be required to present a business combination opportunity to such entities. As a result, there may be actual or potential material conflicts of interest between our sponsor and its affiliates on one hand, and purchasers in this offering on the other. See the sections titled “Proposed Business — Sourcing of Potential Business Combination Targets” and “Management — Conflicts of Interest” for more information.

The underwriters are offering the units for sale on a firm commitment basis. The underwriters expect to deliver the units to the purchasers on or about , 2026

Sole Book-Running Manager

ROTH CAPITAL PARTNERS

, 2026