Primary androgen-deprivation therapy (PADT) is often used to treat clinically localized prostate cancer, but its effects on cause-specific and overall mortality have not been established. Given the widespread use of PADT and the potential risks of serious adverse effects, accurate mortality data are needed to inform treatment decisions. We conducted a retrospective cohort study using comprehensive utilization and cancer registry data from three integrated health plans. All men were newly diagnosed with clinically localized prostate cancer. Men who were diagnosed between 1995 and 2008, were not treated with curative intent therapy, and received follow-up through December 2010 were included in the study (n = 15,170). We examined all-cause and prostate cancer-specific mortality as our main outcomes. We used Cox proportional hazards models with and without propensity score analysis. Overall, PADT was associated with neither a risk of all-cause mortality (hazard ratio [HR], 1.04; 95% CI, 0.97 to 1.11) nor prostate-cancer-specific mortality (HR, 1.03; 95% CI, 0.89 to 1.19) after adjusting for all sociodemographic and clinical characteristics. PADT was associated with decreased risk of all-cause mortality but not prostate-cancer-specific mortality. PADT was associated with decreased risk of all-cause mortality only among the subgroup of men with a high risk of cancer progression (HR, 0.88; 95% CI, 0.78 to 0.97). We found no mortality benefit from PADT compared with no PADT for most men with clinically localized prostate cancer who did not receive curative intent therapy. Men with higher-risk disease may derive a small clinical benefit from PADT. Our study provides the best available contemporary evidence on the lack of survival benefit from PADT for most men with clinically localized prostate cancer.