Recent increases in the average age at first marriage have created an extended period during which young adults frequently continue to socialize with friends, even as romantic ties typically become increasingly serious. Nevertheless, little research has focused on some of the challenges associated with navigating these two social worlds simultaneously. The current study expanded the traditional lens of social learning theory to investigate associations between a range of attitudes and behaviors of friends and a serious form of conflict-intimate partner violence (IPV). Analyses relied on structured survey and in-depth interview data from a longitudinal study of a large, diverse sample of male and female respondents followed across the adolescent to adult transition (n = 928). Consistent with prior work, friends' IPV experience was significantly associated with respondents' own IPV perpetration. Yet the social learning perspective we developed highlighted the importance of considering a broader portfolio of friends' characteristics. Controlling for friends' IPV experience and family background: (a) involvement with friends perceived as more liberal in their attitudes toward dating and sexuality and (b) friends' delinquent behavior were both associated with the odds of reporting IPV. Further, longitudinal analyses showed an effect of variability in friends' delinquency on within-individual changes in IPV across the full study period, suggesting that the association is not due solely to an underlying antisocial propensity. In-depth interviews with a subset of respondents (n = 102) corroborate these results, further illuminate underlying mechanisms, and highlight the dynamic aspects of these forms of social involvement during young adulthood.