Once HIV prevention programs have proven efficacy in research settings, it is important that ongoing data are collected to demonstrate effects in public health applications, yet such evaluations are rare in the published literature. This project describes the adaptation, implementation, and outcome evaluation of the Keep It Up! (KIU!) online HIV prevention intervention as a prevention service delivered in a community-based organization. Compared to pilot research examining KIU! feasibility and efficacy, intervention outcomes were robust to service delivery and client characteristics. In a sample of ethnically and racially diverse young men who have sex with men (N = 343), the intervention produced significant decreases in condomless anal sex acts with casual male partners at the 3-month follow-up compared to baseline (p < .05). In both qualitative and quantitative measures, participants reported that the intervention was highly acceptable and valuable to their sexual health needs.