Objective: From a developmental systems perspective, the origins of maladjusted behavior are multifaceted, interdependent, and may differ at different points in development. Personality traits influence developmental outcomes, as do socialization environments, but the influence of personality depends on the socialization environment, and the influence of the socialization environment varies according to personality. The present study takes a developmental systems approach to investigate pathways through which dispositional traits in childhood might act in concert with peer and parental socialization contexts to predict trajectories of intimate partner aggression (IPA) during emerging adulthood. Method: The study included 466 participants (49% male, 81% European American, 15% African American) from a longitudinal study of social development. Measures of demographics, temperament, personality, parent–child relations, romantic relationships, peer relationships, and IPA were administered between 5 and 23 years of age. The study used latent growth curve analysis to predict variations in trajectories of IPA during early adulthood. Results: Numerous variables predicted risk for the perpetration of IPA, but different factors were associated at the end of adolescence (e.g., psychopathic traits) than with changes across early adulthood (e.g., friend antisociality). Males and individuals with a history of resistance to control temperament showed enhanced susceptibility to social risk factors, such as exposure to antisocial peers and poor parent-adolescent relations. Conclusions: Consistent with a developmental systems perspective, multiple factors, including personality traits in early childhood and aspects of the social environment in adolescence, predict trajectories of IPA during early adulthood through additive, mediated, and moderated pathways. Knowledge of these risk factors and for whom they are most influential could help inform efforts to prevent the emergence and persistence of IPA.