This longitudinal study explored whether students' self-transcendence values predicted their classroom prosocial behavior through perceived teachers' autonomy support. Participants in this three-wave study were 395 fourth and fifth grade students (52% female, mean age = 9.41 at T1). In fourth grade, students reported their self-transcendence values. Four months into fifth grade, students assessed teachers' autonomy support, and their teachers evaluated students' prosocial behavior. Teachers evaluated prosocial behavior again at the end of fifth grade. Results showed self-transcendence values in fourth grade predicted increases in prosocial behavior in fifth grade through perceptions of teachers' autonomy support. These findings expand knowledge of mechanisms underlying relations between self-transcendence values and classroom prosocial behavior. They suggest students are agents capable of shaping their environment.