Background: Increases in externalizing behaviors during the transition to adolescence may put children at risk for developing mental disorders and related problems. Although children's ability to regulate their emotions appears to be a key factor influencing risk for maladjustment, emotion processes during adolescence remain understudied. In this longitudinal study, we examined a multi-level mediational model in which emotion coaching by parents was posited to influence the ability of adolescents to regulate their emotions, which in turn influences their expression of problem behaviors. Methods: We recruited a representative community sample of 244 families with biological sibling pairs comprising a child in late elementary school and a child in middle school. Maternal meta-emotion interviews were coded for mother emotion coaching and adolescent difficulty with anger. Mothers also completed questionnaires on adolescent irritability. Ratings of adolescent problem behaviors were obtained from mother and teacher questionnaires completed at two time points. Using structural equation modeling, constructs were partitioned into components across older and younger siblings to examine shared and nonshared variance and contextual effects. Results: Cross-sectional data indicated that mothers' emotion coaching of anger was related to better anger regulation in adolescent siblings, which was, in turn related to less externalizing behavior. Although support for mediational effects was limited in the longitudinal data, both older and younger siblings' difficulties in regulating anger predicted adolescent externalizing behavior three years later. Additional longitudinal predictors of externalizing behavior were observed for younger siblings. In particular, emotion coaching of anger by mothers was associated with decreased externalizing behavior, while conversely, older siblings' externalizing behavior was associated with increased externalizing behavior in the younger siblings over time. Conclusions: The findings highlight the importance of considering family emotion processes in understanding adolescent problem behavior. Both maternal emotion coaching of adolescent anger and adolescent difficulty in regulating anger influenced adolescent externalizing behavior. Emotion coaching interventions seem worthy of consideration for enhancing the impact of prevention and intervention programs targeting youth externalizing behaviors.