The quality of teacher-student relationships has been shown to relate to adolescents' prosocial behavior, but the motivational mechanisms underlying this association remained unclear. Based on relationships motivation theory (RMT), we examined whether the associations between teacher-student relationships (closeness and conflict) and prosocial behavior are bidirectional, and the mediating role of basic psychological need satisfaction (autonomy, competence, and relatedness need satisfaction) in these links. Data were collected from a sample of 438 secondary school students who completed a survey at two-time points over eight months. The cross-lagged autoregressive model revealed that the relation between close teacher-student relationship and prosocial behavior was bidirectional over time. Moreover, relatedness need satisfaction mediated the positive effect of close teacher-student relationship and the negative effect of teacher-student relationship conflict on adolescents' prosocial behavior. This study highlights the importance of close teacher-student relationship and relatedness need satisfaction to foster adolescents' prosocial behavior.
Keywords: basic psychological need satisfaction; prosocial behavior; relationships motivational theory; teacher-student relationships.