<p>Despite extensive research on the relationship between adolescents’ prosocial behavior and well-being, few studies have examined the relationships between prosocial acts towards different targets (family, friends, and strangers) and both hedonic and eudaimonic well-being over time, especially within the cultural context of China, where relational closeness are highly emphasized. To address this research gap, the present study conducted a longitudinal investigation involving 514 Chinese adolescents (<i>M</i> = 13.75 years, <i>SD</i> = 1.46; 57.2% female) across three time points, each separated by six-month intervals. Cross-lagged panel network analyses revealed the reciprocal relationships between prosocial behavior and well-being, moderated by the relational closeness to the prosocial target. Specifically, the results showed a positive and reciprocal relationships between helping family members and both forms of well-being, as well as between helping friends and eudaimonic well-being. In contrast, while helping strangers did not exhibit a direct reciprocal relationship with well-being, both hedonic and eudaimonic well-being were predictive of prosocial behavior towards strangers. Furthermore, the mediation path analysis elucidated distinct mechanisms: helping family and strangers satisfied autonomy needs, contributing to well-being, whereas helping friends fulfilled relational needs. These findings highlight the mutual interplay between adolescents’ prosocial behavior, particularly towards close relations, and their well-being.</p>