DIVERSIFIED HEALTHCARE TRUST

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 20549

FORM 10-K

For the fiscal year ended December 31, 2025

Commission file number 1-15319

(Exact Name of Registrant as Specified in Its Charter)

Two Newton Place, 255 Washington Street, Suite 300, Newton, MA 02458-1634

(Address of Principal Executive Offices) (Zip Code)

617-796-8350

(Registrant's Telephone Number, Including Area Code)

Securities registered pursuant to Section 12(b) of the Act:

Securities registered pursuant to Section 12(g) of the Act: None

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. Yes x No¨

Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act. Yes¨ No x

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes x No¨

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). Yes x No¨

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 13(a) of the Exchange Act.¨

Indicate by check mark whether the registrant has filed a report on and attestation to its management's assessment of the effectiveness of its internal control over financial reporting under Section 404(b) of the Sarbanes-Oxley Act (15 U.S.C. 7262(b)) by the registered public accounting firm that prepared or issued its audit report.☒

If securities are registered pursuant to Section 12(b) of the Act, indicate by check mark whether the financial statements of the registrant included in the filing reflect the correction of an error to previously issued financial statements.☐

Indicate by check mark whether any of those error corrections are restatements that required a recovery analysis of incentive-based compensation received by any of the registrant's executive officers during the relevant recovery period pursuant to § 240.10D-1(b).☐

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). Yes☐ Nox

The aggregate market value of the voting common shares of beneficial interest, $.01 par value, or common shares, of the registrant held by non-affiliates was approximately $776.9 million based on the $3.58 closing price per common share on The Nasdaq Stock Market LLC on June 30, 2025. For purposes of this calculation, an aggregate of 24,403,883 common shares held directly by, or by affiliates of, the trustees and the executive officers of the registrant have been included in the number of common shares held by affiliates.

Number of the registrant's common shares outstanding as of February 20, 2026:242,121,025

References in this Annual Report on Form 10-K to the Company, DHC, we, us or our mean Diversified Healthcare Trust and its consolidated subsidiaries unless otherwise expressly stated or the context indicates otherwise.

DOCUMENTS INCORPORATED BY REFERENCE

Certain information required by Items 10, 11, 12, 13 and 14 of Part III of this Annual Report on Form 10-K is incorporated by reference to our definitive Proxy Statement for the 2026 Annual Meeting of Shareholders, to be filed with the Securities and Exchange Commission within 120 days after the fiscal year ended December 31, 2025.

Warning Concerning Forward-Looking Statements

This Annual Report on Form 10-K contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995 and other securities laws that are subject to risks and uncertainties. These statements may include words such as “believe”, “expect”, “anticipate”, “intend”, “plan”, “estimate”, “will”, “may” and negatives or derivatives of these or similar expressions. These forward-looking statements include, among others, statements about: our efforts to manage costs and our expectations regarding occupancy and average monthly rates at our Senior Housing Operating Portfolio, or SHOP, communities; market demand and supply for healthcare services for older adults and senior living communities; demand for medical office and life science leased space; our future leasing activity; our leverage; the sufficiency of our liquidity; our liquidity needs and sources; our capital expenditure plans and commitments; our property acquisitions and dispositions; our redevelopment, repositioning and construction activities and plans; and the amount and timing of future distributions.

Forward-looking statements reflect our current expectations, are based on judgments and assumptions, are inherently uncertain and are subject to risks, uncertainties and other factors, which could cause our actual results, performance or achievements to differ materially from expected future results, performance or achievements expressed or implied in those forward-looking statements. Some of the risks, uncertainties and other factors that may cause our actual results, performance or achievements to differ materially from those expressed or implied by forward-looking statements include, but are not limited to, the following:

•The impact of unfavorable market and commercial real estate industry conditions due to possible reduced demand for healthcare related space and senior living communities, uncertainties surrounding interest rates, wage and commodity price inflation, supply chain disruptions, volatility in the public debt and equity markets, changing tariffs and trade policies and related uncertainty, geopolitical instability and tensions, pandemics, any U.S. government shutdown, economic downturns or a possible recession, labor market conditions or changes in real estate utilization, among other things, on us and our managers and other operators and tenants,

•Our senior living operators’ abilities to successfully and profitably operate the communities they manage for us,

•The continuing impact of changing market practices on us and our managers and other operators and tenants, such as delayed recovery of the senior housing industry, reduced demand for leased medical office, life science and other space of ours and residencies at senior living communities and increased operating costs,

•The financial strength of our managers and other operators and tenants,

•Whether the aging U.S. population and increasing life spans of seniors will increase the demand for senior living communities and other medical and healthcare related properties and healthcare services,

•Whether our tenants will renew or extend their leases or whether we will obtain replacement tenants on terms as favorable to us as our prior leases,

•The likelihood that our tenants and residents will pay rent or be negatively impacted by continuing unfavorable market and commercial real estate industry conditions,

•Our managers’ abilities to increase or maintain rates charged to residents of our senior living communities and manage operating costs for those communities,

•Our ability to increase or maintain occupancy at our properties on terms desirable to us,

•Our ability to increase rents when our leases expire or renew,

•Costs we incur and concessions we grant to lease our properties,

•Risk and uncertainties regarding the costs and timing of development, redevelopment and repositioning activities, including as a result of inflation, cost overruns, tariffs, supply chain challenges, labor shortages, construction delays or inability to obtain necessary permits or volatility in the commercial real estate markets,

•Our ability to manage our capital expenditures and other operating costs effectively and to maintain and enhance our properties and their appeal to tenants and residents,

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•Our ability to effectively raise and balance our use of debt and equity capital,

•Our ability to purchase cost effective interest rate caps,

•Our ability to comply with the financial covenants under our debt agreements,

•Our ability to make required payments on our debt,

•Our ability to maintain sufficient liquidity, including the availability of borrowings under our revolving credit facility, and otherwise manage leverage,

•Our credit ratings,

•Our ability to sell properties at prices or returns we target, and the timing of such sales,

•Our ability to sell additional equity interests in, or contribute additional properties to, our existing joint ventures, or enter into additional real estate joint ventures or to attract co-venturers and benefit from our existing joint ventures or any real estate joint ventures we may enter into,

•Our ability to acquire, develop, redevelop or reposition properties that realize our targeted returns,

•Our ability to pay distributions to our shareholders and to maintain or increase the amount of such distributions,

•The ability of The RMR Group LLC, or RMR, to successfully manage us,

•Competition in the real estate industry, particularly in those markets in which our properties are located,

•Government regulations affecting Medicare and Medicaid reimbursement rates and operational requirements,

•Compliance with, and changes to, federal, state and local laws and regulations, accounting rules, tax laws and similar matters,

•Exposure to litigation and regulatory and government proceedings due to the nature of the senior living and other health and wellness related service businesses,

•Actual and potential conflicts of interest with our related parties, including our Managing Trustees, RMR, ABP Trust and others affiliated with them,

•Limitations imposed by and our ability to satisfy complex rules to maintain our qualification for taxation as a real estate investment trust, or REIT, for U.S. federal income tax purposes,

•Acts of terrorism, war or other hostilities, outbreaks of pandemics or other public health safety events or conditions, global climate change or other manmade or natural disasters beyond our control, and

•Other matters.

These risks, uncertainties and other factors are not exhaustive and should be read in conjunction with other cautionary statements that are included in our periodic filings. The information contained elsewhere in this Annual Report on Form 10-K or in our other filings with the Securities and Exchange Commission, or SEC, including under the caption “Risk Factors”, or incorporated herein or therein, identifies other important factors that could cause differences from our forward-looking statements. Our filings with the SEC are available on the SEC’s website at www.sec.gov.

You should not place undue reliance upon our forward-looking statements.

Except as required by law, we do not intend to update or change any forward-looking statements as a result of new information, future events or otherwise.

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Statement Concerning Limited Liability

The Amended and Restated Declaration of Trust establishing Diversified Healthcare Trust, dated September 20, 1999, as amended and supplemented, as filed with the State Department of Assessments and Taxation of Maryland, provides that no trustee, officer, shareholder, employee or agent of Diversified Healthcare Trust shall be held to any personal liability, jointly or severally, for any obligation of, or claim against, Diversified Healthcare Trust. All persons dealing with Diversified Healthcare Trust in any way shall look only to the assets of Diversified Healthcare Trust for the payment of any sum or the performance of any obligation.

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