Recent modelling estimates up to two-thirds of new HIV infections among men who have sex with men occur within partnerships, indicating the importance of dyadic HIV prevention efforts. Although new interventions are available to promote dyadic health-enhancing behaviours, minimal research has examined what factors influence partners’ mutual engagement in these behaviours, a critical component of intervention success. Actor-partner interdependence modelling was used to examine associations between relationship characteristics and several dyadic outcomes theorised as antecedents to health-enhancing behaviours: planning and decision making, communication, and joint effort. Among 270 male-male partnerships, relationship satisfaction was significantly associated with all three outcomes for actors (p = .02, .02, .06 respectively). Latino men reported poorer planning and decision making (actor p = .032) and communication (partner p = .044). Alcohol use was significantly and negatively associated with all outcomes except actors’ planning and decision making (actors: p = .11, .038, .004 respectively; partners: p = .03, .056, .02 respectively). Having a sexual agreement was significantly associated with actors’ planning and decision making (p = .007) and communication (p = .008). Focusing on interactions between partners produces a more comprehensive understanding of male couples’ ability to engage in health-enhancing behaviours. This knowledge further identifies new and important foci for the tailoring of dyadic HIV prevention and care interventions.