Purpose: Contemporary treatment strategies for localized prostate cancer (PCa) have been evolved over time. However, there is little data regarding survival outcomes based on initial treatment by risk group in this new era. This study aims to evaluate survival outcomes among men who underwent observation, radiotherapy, or radical prostatectomy for localized PCa using a population-based cohort. Materials and Methods: The Surveillance, Epidemiology, and End Results (SEER) prostate with watchful waiting dataset (2010–2016) was used. We included men diagnosed with localized PCa and clinical stage T1c-2cN0M0. Other inclusion criteria were age 50–79 years, prostate-specific antigen (PSA) ≤50 ng/mL, and initial treatment with observation (active surveillance/watchful waiting), radiotherapy, or radical prostatectomy. PCa risk was assessed using the D’Amico classification. The primary endpoint was overall survival. Secondary endpoints included PCa-specific survival. Inverse probability of treatment weighting (IPTW)-adjusted Cox proportional hazard regression and competing risk analysis were performed to assess outcomes. Results: After IPTW-adjusting, pseudo-population comprised 521,656 men (observation: 170,428, radiotherapy: 175,628, radical prostatectomy: 175,600) at a median 36.5 month follow-up. Observation demonstrated the lowest 5-year overall survival rate (91.6%) after IPTW-adjusting in comparison to radiotherapy (92.4%) and radical prostatectomy (96.1%, p<0.001). Men who underwent radical prostatectomy had the lowest cumulative PCa-specific and all-cause mortality (p<0.001). Compared to observation, radiotherapy (sub-distribution hazard ratio [sHR], 0.89; 95% CI, 0.81–0.97; p=0.012) and radical prostatectomy (sHR, 0.46; 95% CI, 0.41–0.52; p<.001) had a lower risk of PCa-specific mortality in competing risk analysis after adjustment for all other factors and other-cause death. Conclusions Intermediate-term mortality risk in men with localized PCa were lower with active treatments compared to observation-especially for intermediate- and high-risk disease. However, observation represents a safe management strategy in men within the low-risk group.