Childhood adversities have been linked to externalizing problems in adolescence. However, studies focusing on early adolescence are rare. Even less empirical attention has been given to the unique and joint influences of children's and maternal childhood adversity on children's externalizing behavior, particularly with a keen focus on the nature of adversities. This study examined the influences of children's and maternal childhood adversities on children's externalizing problems in early adolescence, delineating domains of childhood adversities. The data came from a longitudinal study of teen mothers and their children (N = 495). The findings reveal children's childhood maltreatment experience was associated with externalizing problems in early adolescence. Further, maternal childhood maltreatment functioned as an additive risk source for target adolescents' externalizing problems. These findings support the need to delineate adversity domains to further clarify the link between childhood adversity and externalizing problems. Our findings also support a multigenerational approach in pediatric settings.