Most HIV infections among young men who have sex with men (YMSM) occur within primary partnerships. Research on YMSM's knowledge, motivation, and behavioral skills regarding relationship-related HIV prevention, and how these correspond to HIV risk and partnership characteristics, is limited. We examined links among the Relationship-Oriented Information- Motivation-Behavioral Skills (RELO-IMB) model, relationship characteristics, and HIV risk in 96 YMSM. Condomless sex with a primary partner was associated with low relationship-related HIV preventive information, motivation, and behavioral skills. Lack of HIV testing and alcohol use before sex were associated with low behavioral skills. In multivariate analyses, behavioral skills were the only consistent predictor of these outcomes. Regarding relationship characteristics, feeling trapped in the relationship or being physically abused by a partner was associated with low motivation and behavioral skills. The RELO-IMB model can be used to understand HIV risk in relationships and points to targets for relationship-specific HIV prevention education for YMSM.