BackgroundResearch suggests that positivity and self-efficacy beliefs may impact adaptive behavior and developmental outcomes, such as social adjustment and subjective wellbeing. The present study explored the effect of positive dimensions (positivity and self-efficacy beliefs) and individual characteristics (gender, type of country, age, and sexual orientation) on family cohesion and flexibility in a group of Colombian and Italian young adults.MethodAn online survey was administered to 949 Colombian and 2,073 Italian people aged between 18 and 40 years (Mage = 24.3; SDage = 4.5; 67% women). A mediational model was performed to test the influence of positivity on family functioning via the mediational role of self-efficacy beliefs, analyzing the moderated effects of gender, type of country, sexual orientation, and age.ResultsFilial self-efficacy mediated the effect of positivity on family functioning, showing stronger paths in men and Colombian participants than in women and Italian counterparts. Regulatory self-efficacy mediated the associations between positivity and family functioning for both genders and types of countries.ConclusionThe results suggest that positivity and self-efficacy beliefs may allow families to engage in more adaptive family functioning across countries and genders. Further research should focus on implications from a cross-national perspective to examine other culture-specific factors that may impact family adjustment.