Hospital funding reforms for prostate cancer surgery may have altered management of localized prostate cancer in the province of Ontario, Canada. To determine whether changes in hospital funding policy aimed at improving health care quality and value were associated with changes in the management of localized prostate cancer or the characteristics of patients receiving radical prostatectomy (RP) for localized prostate cancer. This population-based, interrupted time series study used linked population-based administrative data regarding adults in Ontario with incidental localized prostate cancer and those who underwent RP for localized prostate cancer. Patients who underwent RP were compared with patients who underwent surgical procedures for localized renal cell carcinoma, which was not included in the policy change but was subjected to similar secular trends and potential confounders. Monthly outcomes were analyzed using interventional autoregressive integrated moving average models. Data were collected from January 2011 to November 2017 and analyzed in January 2019. Funding policy change in April 2015 from flexible block funding for all hospital-based care to prespecified payment amounts per procedure for treatment of localized prostate cancer, coupled with the dissemination of a diagnosis-specific handbook outlining best practices. Initial management (RP vs radiation therapy vs active surveillance) and tumor risk profiles per management strategy among incident cases of localized prostate cancer. Additional outcomes were case volume, mean length of stay, proportion of patients returning to hospital or emergency department within 30 days, proportion of patients older than 65 years, mean Charlson Comorbidity Index, and proportion of minimally invasive surgical procedures among patients undergoing RP for localized prostate cancer. A total of 33 128 patients with incident localized prostate cancer (median [interquartile range (IQR)] age, 67 [61-73] years; median [IQR] cases per monthly observation interval, 466 [420-516]), 17 159 patients who received radical prostatectomy (median [IQR] age, 63 [58-68] years; median [IQR] cases per monthly observation interval, 209 [183-225]), and 5762 individuals who underwent surgery for renal cell carcinoma (median [IQR] age, 62 [53-70] years; median [IQR] cases per monthly observation interval, 71 [61-77]) were identified. By the end of the observation period, radical prostatectomy and radiation therapy were used in comparable proportions (30.3% and 28.9%, respectively) and included only a small fraction of low-risk patients (6.4% and 2.9%, respectively). No statistically significant association of the funding policy change with most outcomes was found. The implementation of funding reform for hospitals offering RP was not associated with changes in the management of localized prostate cancer, although it may have encouraged more appropriate selection of patients for RP. Mostly preexisting trends toward guideline-conforming practice were observed. Co-occurring policy changes and/or guideline revisions may have weakened signals from the policy change.