This study used the Popular Opinion Leader (POL) model to reduce stigma among service providers. The authors focused on the dissemination of intervention messages from trained POL providers to their peer providers and the change of intervention outcome over time. The sample included 880 service providers from 20 intervention hospitals. The levels of message diffusion, prejudicial attitude toward people living with HIV (PLH), and avoidance intent to serve PLH were self-reported at baseline, 6 months, and 12 months. At 6 months, POL providers showed a significantly higher level of message diffusion and lower levels of prejudicial attitude and avoidance intent than non-POL providers. However, such discrepancies diminished at 12 months. The results support the utility of the POL model in stigma reduction interventions. The observed changes were documented not only in POLs but also in non-POLs after a certain period of time. This finding informed the design and implementation of future stigma reduction efforts and POL intervention programs.