CONTEXT: Androgen receptor signaling inhibitor (ARSi) agents are emerging as standard treatments for prostate cancer across the disease spectrum, but much remains unknown regarding how their side-effect profiles compare. OBJECTIVE: To systematically evaluate the literature regarding adverse events (AEs) between the ARSi drugs abiraterone, apalutamide, darolutamide, and enzalutamide in the treatment of metastatic castration-resistant prostate cancer (mCRPC), nonmetastatic CRPC (nmCRPC), and metastatic castration-sensitive prostate cancer (mCSPC). EVIDENCE ACQUISITION: PubMed, Web of Science, and Embase were queried for double-blind, randomized controlled trials (RCTs) of ARSi therapy up to September 2022 according to the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) statement. Two teams reviewed titles and abstracts, and 14 RCTs were included for analysis. EVIDENCE SYNTHESIS: Forest plots were used to summarize risk ratios for the most common AEs. According to surface under the cumulative ranking curve (SUCRA) values, enzalutamide was ranked as the most toxic treatment regarding hypertension outcomes (SUCRA 0%, most likely to be the bottom-ranked treatment) in both mCRPC and nmCRPC (SUCRA 0%). Enzalutamide was also ranked as the most toxic regarding headache across all prostate cancer entities (SUCRA 0%, for mCRPC, 1% for nmCRPC, and 3% for mCSPC). CONCLUSIONS: Our findings suggest that the ARSi side-effect profiles do not significantly differ, except that enzalutamide was ranked the most toxic regarding hypertension in mCRPC and nmCRPC, and the most toxic regarding headache across all prostate cancer settings. These results highlight the importance of close blood-pressure monitoring for enzalutamide, and future research should explore possible connections between cardiovascular and neurological risk with ARSi therapy. In addition, these comparisons rely on the validity of cross-trial comparisons. PATIENT SUMMARY: We reviewed the side-effect profiles of second-generation antiandrogen drugs for the treatment of prostate cancer. Side effects were similar, apart from higher risk of high blood pressure and headache risk with enzalutamide.