The K–9 Hero Act of 2026 proposes to establish a federal grant program aimed at assisting with the veterinary expenses of retired Federal working dogs. This initiative addresses findings that highlight the significant number of working dogs in federal service and the financial burden on owners for their retired companions' medical care. Currently, owners often rely on underfunded nonprofit organizations to cover these costs. Under this bill, the Secretary of Defense and the Secretary of Homeland Security will jointly administer a program to award grants to eligible nonprofit organizations. These organizations must primarily focus on providing care or financial assistance for the medical needs of retired Federal working dogs. Grants are capped at $1,000,000 per fiscal year per organization. These grants are exclusively for "covered medical expenses," encompassing treatment for injuries, illnesses, and necessary medical procedures, irrespective of when the condition manifested. To ensure accountability, the Secretaries are required to develop data on health outcomes, monitor funding needs, and collect information from grant recipients, with nonprofits submitting annual reports. The bill authorizes an appropriation of $5,000,000 annually for fiscal years 2027 through 2031 to fund this crucial program, ensuring sustained support for the welfare of these retired service animals.