Purpose: To assess if high school students' leisure-time physical activity is predicted by their perception of the motivational climate, their perceived competence, and their achievement goals in physical education (PE) and if these variables interact with each other. Methods: A sample of 843 high school students completed self-reported questionnaires in the middle and at the end of the school year. The data were analyzed by structural equation modeling and latent moderated structural equations. Results: Leisure-time physical activity was positively predicted by students' performance-approach goals and perceived competence in PE and by the interaction between their perceived competence and their adoption of mastery goals. Discussion/Conclusion: Only individual variables in PE were related to leisure-time physical activity. The significant interaction effect between students' mastery goals and perceived competence in PE suggests that teachers need to foster students' perceptions of competence. The authors therefore discuss the scope of the results with regard to pedagogical practices.