As technology has been developing by leaps and bounds, concerns regarding adolescent online behavioral patterns have garnered significant attention. Nevertheless, current research exhibits limitations in both perspective and depth. Consequently, this study introduces a moderated mediation model to investigate whether the mediating effect of self-efficacy and the moderating effect of emotional regulation strategies are valid in the relationship between family communication patterns and adolescent online prosocial behavior. A questionnaire survey encompassing 1183 adolescents across 12 schools in three cities of mainland China was conducted. The findings reveal that conversation orientation contributes to the augmentation of adolescents’ self-efficacy and online prosocial behavior, whereas conformity orientation follows a reversed trend. Furthermore, self-efficacy serves as a mediator in the relationship between conversation orientation and conformity orientation, influencing adolescent online prosocial behavior in both positive and negative manners. Additionally, this study underscores the significance of emotion regulation strategies; cognitive reappraisal not only reinforces the positive effects of conversation orientation, but also mitigates the adverse effects of conformity orientation, while expressive suppression demonstrates the inverse effect. This research yields a comprehensive and insightful understanding of adolescent online prosocial behavior, furnishing a valuable theoretical foundation for future research and practice in family education.