This randomized controlled trial tested the efficacy of an HIV prevention intervention to increase condom use and HIV testing among Spanish-speaking, heterosexually active immigrant Latino men. A community-based participatory research partnership developed the intervention and selected the study design. Following baseline data collection, 142 immigrant Latino men were randomized to the HIV prevention intervention or the cancer education intervention. Three-month follow-up data were collected from 139 participants, for a 98% retention rate. Mean age of participants was 31.6 years and 60% reported being from Mexico. Adjusting for baseline behaviors, relative to their peers in the cancer education comparison, participants in the HIV prevention intervention were more likely to report consistent condom use and receiving an HIV test. Community-based interventions for immigrant Latino men that are built on state of the art prevention science and developed in partnership with community members can greatly enhance preventive behaviors and may reduce HIV infection.