Oncology Institute, Inc.

This Proxy Statement is furnished in connection with the solicitation of proxies by the Board of Directors (the “Board of Directors” or the “Board”) of The Oncology Institute, Inc., a Delaware corporation, for use at the Annual Meeting of Stockholders. This Proxy Statement and related materials are first being sent or made available to stockholders on or about April 30, 2026. References in this Proxy Statement to “we,” “us,” “our,” or the “Company” refer to The Oncology Institute, Inc. and its consolidated subsidiaries, and references to the “Annual Meeting” are to our 2026 annual meeting of stockholders. When we refer to the Company’s fiscal year, we mean the annual period ended on December 31, 2025. This proxy statement covers our 2025 fiscal year, which was from January 1, 2025 through December 31, 2025, or fiscal 2025. This summary highlights information contained elsewhere in this proxy statement and does not contain all of the information that you should consider. You should read the entire proxy statement carefully before voting.

Our Annual Meeting

At the Annual Meeting, the stockholders of the Company will be asked to vote on the four proposals below. Your vote is very important. Accordingly, whether or not you plan to attend the Annual Meeting, you should vote by using one of the methods described in these proxy materials. You may vote your shares at the Annual Meeting by voting via the Internet or by telephone as described in these proxy materials or by having your shares represented at the Annual Meeting by a valid proxy. If your shares are not registered directly in your name (e.g., you hold your shares in a stock brokerage account or through a bank or other holder of record), you may vote by following the instructions detailed on the notice or voting instruction form you receive from your broker or other nominee. A list of all stockholders entitled to vote at the Annual Meeting will be available for inspection at our executive offices.

Any stockholder who executes and delivers a proxy has the right to revoke it at any time before it is exercised by delivering to the Chief Legal Officer of the Company an instrument revoking it or a duly executed proxy bearing a later date, or by attending the Annual Meeting and voting. Subject to revocation, the proxy holders will vote all shares represented by a properly executed proxy received in time for the Annual Meeting in accordance with the instructions on the proxy. If no instruction is specified with respect to a matter to be acted upon, the shares represented by the proxy will be voted in accordance with the recommendation of the Board of Directors.

The accompanying proxy is solicited on behalf of the Board for use at the Annual Meeting, and accordingly, the Company will pay the cost of soliciting proxies for the Annual Meeting. We have engaged Morrow Sodali LLC as our solicitation agent to assist in the solicitation of proxies for the Annual Meeting. We have agreed to pay Morrow Sodali LLC, the solicitation agent, a fee of $12,500, plus telephone solicitation fees. We will also reimburse the solicitation agent for expenses related to certain ancillary services and its other reasonableout-of-pocket expenses, and we will indemnify the solicitation agent and its affiliates against certain claims, liabilities, losses, damages and expenses. We will also reimburse banks, brokers and other custodians, nominees and fiduciaries representing beneficial owners of shares of our Common Stock for their expenses in forwarding soliciting materials to beneficial owners of Common Stock and in obtaining voting instructions from those owners. Our directors, officers and employees may also solicit proxies by telephone, by facsimile, by mail, on the Internet or in person. They will not be paid any additional amounts for soliciting proxies.

Prior Proposal

At the Company’s 2025 annual meeting of stockholders, stockholders approved a proposal to amend the Company’s Certificate of Incorporation to effect a reverse stock split of the Company’s Common Stock if deemed appropriate by the Board (the “2025 Reverse Stock Split Proposal”). Following that approval, the Board determined not to exercise its discretion to implement the reverse stock split. The Company has since regained and maintained compliance with the Nasdaq Capital Market’s minimum bid price requirement without the need for a reverse stock split, and the Common Stock continues to be listed on the Nasdaq Capital Market. No reverse stock split proposal is being submitted for stockholder approval at our 2026 Annual Meeting.

Quorum Requirements

In order to constitute a quorum for the conduct of business at the Annual Meeting, a majority of the shares of the Common Stock issued and outstanding and entitled to vote at the Annual Meeting must be present at the meeting or represented by proxy. Shares represented by proxies that reflect abstentions or brokernon-votes will be counted as shares that are present and entitled to vote for purposes of determining the presence of a quorum.

Each share of our Common Stock outstanding on the record date is entitled to one vote on each of the eight director nominees. Each share of our Common Stock outstanding on the record date is entitled to one vote on each other matter. For the election of directors, the nominees to serve as directors will be elected by a plurality of the votes cast by the stockholders entitled to vote at the election. You may vote “For” or “Withhold” with respect to the director nominees. Votes that are withheld will be excluded entirely from the vote with respect to the nominee from which they are withheld and will have no effect on the election of directors. With respect to Proposal 2 and Proposal 3, approval requires the affirmative vote of a majority of the votes properly cast “For” and “Against” the proposal. Abstentions will have the same effect as a vote against each of Proposal 2 and Proposal 3 because they are counted for purposes of determining the presence of a quorum but are not counted as in favor of the proposal. With respect to Proposal 4, the frequency option receiving the greatest number of votes cast will be considered the stockholders’ preferred frequency. Abstentions will be excluded entirely from the vote so will have no effect on Proposal 4.

Brokernon-votes occur when a beneficial owner of shares held in “street name” does not give instructions to the broker, bank or other nominee holding the shares as to how to vote on matters deemed“non-routine” by stock exchange rules and regulations. Proposal 2 regarding ratification of the appointment of our independent auditors is a routine matter. If your shares are held in an account at a bank or brokerage firm, that bank or brokerage firm may vote your shares of Common Stock on Proposal 2. Accordingly, we do not expect there to be any brokernon-votes for Proposal 2. However, if your shares are held in an account at a bank or brokerage firm, that bank or brokerage will not be permitted to vote your shares of Common Stock with respect to Proposals 1, 3 or 4 unless you provide instructions as to how your shares should be voted. Accordingly, we encourage you to vote promptly, even if you plan to attend the virtual Annual Meeting. In tabulating the voting results for any particular proposal, shares that constitute brokernon-votes are not considered entitled to vote on that proposal. Brokernon-votes, if any, will have no effect on each of Proposals 1, 3 and 4.

Additional Information Regarding the Internet Availability of Our Proxy Materials

We are pleased to take advantage of SEC rules that allow companies to furnish their proxy materials over the Internet. Accordingly, we sent to the majority of our stockholders an Internet Availability Notice regarding the Internet availability of the proxy materials for this year’s Annual Meeting. Other stockholders were instead sent paper copies of the proxy materials accessible on the Internet upon their express election. Instructions on how to access the proxy materials over the Internet or to request a paper copy can be found in the Internet Availability Notice. In addition, stockholders may request to receive proxy materials in printed form by mail or electronically by email on an ongoing basis by going to www.investorelections.com/TOI and following the instructions or calling 1-866-648-8133. A stockholder’s election to receive proxy materials by mail ore-mail will remain in effect until the stockholder terminates or changes such election.

Please note that you cannot vote your shares by filling out and returning the Internet Availability Notice. The Internet Availability Notice does, however, include instructions on how to vote your shares.

If your shares are registered directly in your name with our transfer agent, you are considered, with respect to those shares, the “stockholder of record.” In that case, either the Internet Availability Notice or the Notice of Annual Meeting, this proxy statement and our Annual Report on Form 10-K for the fiscal year ended December 31, 2025 have each been sent directly to you.

If your shares are held in a stock brokerage account or by a bank or other holder of record, you are considered the “beneficial owner” of shares held in street name. In such case, either a notice similar to the Internet Availability Notice or the Notice of Annual Meeting, this proxy statement and our Annual Report on Form 10-K for the fiscal year ended December 31, 2025 should have been provided (or otherwise made available) to you by your broker, bank or other holder of record who is considered, with respect to those shares, the stockholder of record. As the beneficial owner, you have the right to direct your broker, bank or other holder of record on how to vote your shares by following their instructions for voting.