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**Background:** The use of androgen receptor signaling inhibitors, including apalutamide, in combination with androgen deprivation therapy is recommended for the treatment of metastatic castration-sensitive prostate cancer (mCSPC) and non-metastatic castration-resistant prostate cancer (nmCRPC). **Objective:** To describe real-world treatment patterns and clinical outcomes among patients with mCSPC or nmCRPC who initiated apalutamide in the United States. **Methods:** A retrospective cohort study of patients with mCSPC or nmCRPC who initiated apalutamide was conducted using electronic medical record data from US community-based urology practices (Feb. 1, 2017–April 1, 2022). Persistence with apalutamide was reported at 6-, 12-, and 18-months post treatment initiation. Clinical outcomes described up to 24 months after apalutamide initiation using Kaplan-Meier analyses included progression to castration resistance, castration resistance-free survival (CRFS), and metastasis-free survival (MFS). Outcomes were reported separately based on mCSPC or nmCRPC status and race (ie, Black or non-Black). **Results:** This study included 589 patients with mCSPC (mean age, 75.9 years) and 406 patients with nmCRPC (mean age, 78.8 years). Using a treatment gap of >90 days, persistence with apalutamide at 12 months remained high for both the mCSPC (94.9%) and nmCRPC (92.7%) cohorts, and results were descriptively similar among Black and non-Black patients, and when a treatment gap of >60 days was considered. In patients with mCSPC, overall progression to castration resistance rates at 12 and 24 months were 20.9% and 33.5%, and overall CRFS rates were 76.2% and 62.0%, respectively. In patients with nmCRPC, overall MFS rates at 12 and 24 months were 89.7% and 75.4%, respectively. Rates of these clinical outcomes were descriptively similar between Black and non-Black patients. **Discussion:** While clinical trials have demonstrated the efficacy and safety of apalutamide, there is limited real-world data describing treatment persistence and clinical outcomes among patients with mCSPC and nmCRPC who initiated apalutamide. **Conclusions:** In this real-world study of patients with mCSPC or nmCRPC initiated on apalutamide, treatment persistence was high and apalutamide demonstrated robust real-world effectiveness with respect to progression to castration resistance, CRFS, and MFS, overall and among Black and non-Black patients.