This study evaluated the effectiveness of a community-based peer intervention to reduce HIV risk among men who have sex with men (MSM) in Sichuan province, China. The intervention was based on the Popular Opinion Leader framework, in which respected MSM peer leaders attempted to change MSM community norms related to sexual behavior and HIV risk. The intervention was conducted in a metropolitan city, with a matched city in the same province serving as a comparison. We conducted a baseline survey of HIV risk behaviors with 200 MSM per city, provided the intervention for 12 months in the treatment city, and conducted a post-treatment survey of an independent sample of 200 MSM per city. In the intervention city at post-treatment, we observed reduced unprotected anal intercourse during the last 3 sex episodes with a primary male partner (AOR = 0.31, 95% CI = 0.17-0.57), reduced anal intercourse during the last 3 sex episodes with male casual or commercial partners (AOR = 0.15, 95% CI = 0.07-0.35), increased condom use during last sex episode with a primary male partner (AOR = 3.33, 95% CI = 1.86-5.98), and increased condom use during last sex episode with male casual or commercial partners (AOR = 3.78, 95% CI = 1.07-13.41). In the control city at post-treatment, we observed decreased condom use with male casual or commercial partners (AOR = 0.39, 95% CI = 0.15-0.99). Findings suggest that a community-based intervention involving popular opinion leaders can decrease sexual risk behavior among MSM in China.