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BACKGROUND Adherence to oral cancer drugs is suboptimal. The Oncology Care Model (OCM) offers oncology practices financial incentives to improve the value of cancer care. We assessed the impact of OCM on adherence to oral cancer therapy for chronic myelogenous leukemia (CML), prostate cancer, and breast cancer. METHODS Using 2014-2019 Medicare data, we studied chemotherapy episodes for Medicare fee-for-service beneficiaries prescribed tyrosine kinase inhibitors (TKIs) for CML, antiandrogens (ie, enzalutamide, abiraterone) for prostate cancer, or hormonal therapies for breast cancer, in OCM-participating and propensity-matched comparison practices. We measured adherence as the proportion of days covered and used difference-in-difference (DID) models to detect changes in adherence over time, adjusting for patient, practice, and market-level characteristics. RESULTS There was no overall impact of OCM on improved adherence to TKIs for CML (DID=; -0.3%, 90%confidence interval [CI] =; -1.2%, 0.6%), antiandrogens for prostate cancer (DID=; 0.4%, 90%CI =; -0.3%, 1.2%), or hormonal therapy for breast cancer (DID=; 0.0%, 90%CI =; -0.2%, 0.2%). Among episodes for Black beneficiaries in OCM practices, for whom adherence was lower than for White beneficiaries at baseline, we observed small improvements in adherence to high cost TKIs (DID=; 3.0%, 90%CI =; 0.2%, 5.8%) and antiandrogens (DID=; 2.2%, 90%CI =; 0.2%, 4.3%). CONCLUSIONS OCM did not impact adherence to oral cancer therapies for Medicare beneficiaries with CML, prostate cancer, or breast cancer overall, but modestly improved adherence to high-cost TKIs and antiandrogens for Black beneficiaries, who had somewhat lower adherence than White beneficiaries at baseline. Patient navigation and financial counseling are potential mechanisms for improvement among Black beneficiaries.