This study investigated the extent to which students' social-emotional basic psychological need satisfaction (of social-emotional autonomy, social competence, relatedness with students, and relatedness with teachers) is associated with their prosocial motivation and, in turn, behavioral and emotional well-being outcomes. For motivation, autonomous prosocial motivation and controlled prosocial motivation (by way of introjected and external regulation) were examined. Behavioral outcomes comprised prosocial behavior and conduct problems reported by parents/carers, and emotional well-being were positive and negative affect reported by students. With data from 408 secondary school students (and their parents/carers), structural equation modeling showed that perceived autonomy was associated with lower negative affect. Perceived social competence was associated with greater autonomous prosocial motivation, lower external prosocial regulation, greater positive affect, and lower negative affect. Relatedness with teachers was associated with greater autonomous prosocial motivation. In turn, autonomous prosocial motivation was associated with greater prosocial behavior, whereas external prosocial regulation was associated with lower prosocial behavior. Introjected prosocial regulation was only associated with greater negative affect. The results hold implications for promoting social and emotional competence among students.