The literature shows that impulsivity, prevalent in adolescence, is negatively linked with a variety of psychosocial factors (e.g., positive interpersonal relationships, emotion regulation); however, there is limited research examining the relative contribution of multiple factors for this trait nor exploring how these factors influence the associations between impulsivity and risk-related outcomes. Drawing on multiple components of the unified theory of development (i.e., psychological variables, peers subsystem, community subsystem, family processes subsystem), this cross-sectional study aims to identify explanatory psychosocial variables (i.e., early memories of warmth and safeness, rational decision-making style, resilience, emotion regulation, coping, parental attachment, social group attachment, satisfaction with school and family-related variables) that are negatively related with impulsivity, in younger (13–15) and older (16–19 years) adolescents, and explore their moderating role in the associations between this trait and some risk-related outcomes (i.e., verbal aggression, anger, self-harm, other high-risk behaviors). A representative sample of 6894 adolescents (52.9% female) living in the Azores (Portugal), with ages ranging from 13 to 19 (M = 15.4), was used. Two stepwise multiple regressions, one for each age group, revealed that only emotion regulation, parental attachment, and social group attachment had a negative effect on impulsivity in both age groups; additionally, satisfaction with teachers also had this effect in younger adolescents. The first three variables weakened the positive associations between impulsivity and the risk-related outcomes. These results suggest that the psychological system and all subsystems of the social context measured play a relevant role in explaining adolescent impulsivity and that it may be reduced by promoting emotion regulation, positive parenting practices, healthier relationships with peers, and healthier relationships with teachers.