Fear of negative evaluation and prosocial behavior have been identified as predictive factors influencing the development of loneliness in adolescence, representing typical factors in the cognitive and behavioral processes of re-affiliation. The elucidation of plausible direct and indirect pathways linking these pivotal factors to adolescents’ loneliness need further exploration. This study aimed to investigate the direct and indirect relationships between the fear of negative evaluation, prosocial behavior, and adolescents’ loneliness through the lens of developmental changes. A total of 533 adolescents (49.0% girls, Mage = 15.18 years, SD = 0.71) participated in this longitudinal study, assessed at three timepoints over a span of two years with 12-month intervals. Latent growth modeling uncovered direct associations between the developmental trajectories of both fear of negative evaluation and prosocial behavior with the developmental trajectory of adolescents’ loneliness. The developmental trajectory of fear of negative evaluation exhibited an indirect association with the developmental trajectory of loneliness through the mediating role of prosocial behavior. These findings highlighted the roles of cognitive and behavioral re-affiliation processes, both independently and as mediators, in influencing adolescent loneliness, suggesting that interventions aimed at reducing fear of negative evaluation and promoting prosocial behavior could effectively mitigate adolescents’ loneliness.
