The current study examined the relevance of relationship functioning to partners' agreement or consensus about joint effort surrounding COVID-19 prevention. Interdependence theory has been widely used to understand how relationship partners influence health behavior, including how sexual minority male (SMM) couples regulate HIV risk. Couples with better relationship functioning tend to be more successful at negotiating joint (shared) goals and subsequently accomplishing them. The study recruited 134 cis-male, SARS-CoV-2 negative adults in relationships with cis-male partners from phone-based social networking applications. Participants completed an online survey assessing relationship functioning (Perceived Relationship Components Questionnaire), COVID-19 prevention behaviors, and risk perceptions. Partners' consensus around joint COVID-19 prevention effort was assessed using an adapted version of the Preferences for Sexual Health Outcomes scale. Path analyses indicated that consensus for joint prevention effort predicted social distancing (B = 0.23; p = .001) and the number of other COVID-19 prevention behaviors engaged in (B = 0.17; p = .003) above and beyond perceived risk and relationship functioning. Relationship satisfaction predicted higher levels of consensus for joint COVID-19 prevention effort (B = 0.40; p = .029). Findings suggest that the theoretical foundations of successful HIV prevention interventions that utilize joint goal formation may generalize to the prediction of COVID-19 prevention behavior and may be leveraged to mitigate the risk of SARS-CoV-2 infection among SMM in relationships. Interventions that overlook the potential for dyadic regulation of health behavior may miss opportunities to capitalize on shared coping resources and fail to address relational barriers to prevention.