This short-term longitudinal investigation examined the 2-year stability of adolescents' prosocial behavior toward mothers and fathers and the predictive role of attachment, conflict, and parental influence in adolescents ' prosocial behavior. At Time 1, adolescents (n = 129) in Grades 6, 8, and 10 and their mothers (n = 126) and fathers (n = 104) completed several questionnaires during two in-home visits. Two years subsequently, families (n = 42) completed the same measures from Time 1. In general, adolescents reported less affectionate behavior and helpfulness toward fathers and mothers during early adolescence and middle adolescence. Parents reported no change in adolescents' behavior. Adolescents' affection and helpfulness remained stable across 2 years. For adolescent reports, attachment predicted affection, whereas paternal influence predicted helpfulness toward fathers. For parent reports, conflict and parental influence predicted adolescent affection. The use of the relational approach for understanding adolescent prosocial behavior is discussed.Within close relationships, children learn and develop many important social skills, such as prosocial behavior. Prosocial behavior is defined as voluntary behavior intended to benefit another (Eisenberg, 1982) and has been studied from several perspectives, most often from a dispositional or a situational perspective. A personal relationships approach was employed for the present study. Adolescents' prosocial behavior toward parents is proposed to be embedded in parent/adolescent relationships; therefore, variation in adolescents' prosocial behavior toward parents is tied to variation in their relationships with parents.From a personal relationships perspective, the context of a close, interdependent relationship is central to understanding individual behavior within 226