This study examines the interaction between gender and classroom social goal structures and the impact they have on children's prosocial behaviors and classroom adjustment. Specifically, classroom social goal structures (consisting of prosocial and compliance goal structure) are the degree to which focal social goals are presented in classrooms. Numerous previous studies have tested the gender differences in social outcomes; however, the results of such past studies have been mixed, as some detected gender differences while others did not. This suggests the existence of moderator variables. Consequently, in this research, we focused on classroom-level moderators in the relationship between gender and social outcomes. We analysed a sample of 3,609 Japanese public elementary school children from 114 classrooms, and we detected the presence of cross-level interactions and found that classroom social goal structures can promote or degrade boys' social outcomes.