Using data from 4047 adolescents in three countries, this study was designed to investigate the associations between two important components of the learning process: academic motivation and student engagement. To increase the precision and accuracy of these analyses, preliminary analyses were conducted to identify the optimal measurement structure of both constructs, leading us to retain a bifactor exploratory structural equation modeling representation of academic motivation and of a partial bifactor confirmatory factor analytic representation for student engagement. Our main analyses revealed that academic motivation factors were able to explain almost 66% of the variance in global levels of engagement, and between 5% and 35% of the variance in specific levels of engagement. Finally, mediation analyses supported the role of emotional engagement as a mediator of the association between academic motivation and global and specific behavioral forms of engagement.