This study evaluated the survival outcomes of young (<50 years) and elderly patients (>80 years) with high-risk prostate cancer (PCa) postradical local treatments.We identified <50 and >80-year-old patients with high-risk PCa between 2004 and 2015 in the Surveillance, Epidemiology, and End Results database. The patients aged 65 and 66 years were also identified as the control group. The propensity-score matching method was adopted to compare the young and elderly patients with the control group. Kaplan-Meier analysis and Cox regression were conducted to evaluate the PCa-specific survival (PCSS) and overall survival.A total of 17726 patients were identified, and 3355 were under 50 years old, whereas 4798 of them were >80 years old. The young patient group (<50 years) had similar PCSS with the control group (65-66 years) in both the overall cohort (hazard ratio [HR]: 0.88, 95% confidence interval [CI] [0.73-1.06], P = 0.132) and matched cohort (HR: 0.96, 95% CI [0.74-1.24], P = 0.527). Young patients with both high-risk and very high-risk PCa after radical prostatectomy (RP) treatment had apparent longer mean cancer-specific survival time than those after external-beam radiotherapy (EBRT) and/or brachytherapy (BT) treatment (high-risk group: 153.38 ± 0.82 months vs. 149.72 ± 3.03 months; very high-risk group: 148.3 ± 1.84 months vs. 139.33 ± 3.25 months). For the elderly patients (>80 years), the PCSS outcomes were significantly worse than the control group (65-66 years) in both overall cohort (HR: 2.69, 95% CI [2.31-3.13], P < 0.001) and matched cohort (HR: 1.61, 95% CI [1.34-1.94], P < 0.001). Patients receiving RP treatment had similar PCSS outcomes with those receiving EBRT and/or BT in the high-risk PCa group (139.45 ± 9.98 months vs. 139.41 ± 1.84 months), and better PCSS in very high-risk PCa group (132.73 ± 13.56 months vs. 128.82 ± 3.43 months).The PCSS outcomes of young PCa patients (<0 years) were identical to those of the control group (65-66 years). RP had similar or better PCSS benefits than EBRT and/or BT in both young (<50 years) and elderly patients (>80 years).