This study examined the associations between reasoning during inter-parental conflict and autonomous adolescent conflict negotiation with peers over time. Participants included 133 adolescents and their parents, peers, and romantic partners in a multimethod, multiple reporter, longitudinal study. Inter-parental reasoning at adolescent age of 13 predicted greater autonomy and relatedness in observed adolescent-peer conflict one year later and lower levels of autonomy undermining during observed romantic partner conflict five years later. Inter-parental reasoning also predicted greater satisfaction and affection in adolescent romantic relationships seven years later. Findings suggest that autonomy-promoting behaviors exhibited in the interparental context may influence adolescents' own more autonomous approaches to subsequent peer and romantic conflict. Possible explanatory models are discussed, including social learning theory and attachment theory. (Contains 1 table and 1 figure.)