The current study investigated the mediating role of academic engagement in the association between the teacher--student relationship and academic achievement, and whether self-control moderates the mediating process. The sample consisted of 1411 Chinese adolescents (M[subscript age] = 16.77 years, 543 boys) aged between 11 and 19 years. Self-reported questionnaires were used to collect data. The results show that (1) the teacher-student relationship has a significant positive predictive effect on adolescents' academic achievement; (2) academic engagement has a positive mediating effect between the teacher-student relationship and academic achievement; and (3) the indirect effect of the teacher-student relationship on adolescents' academic achievement through academic engagement is moderated by self-control, in which self-control plays a role as a protective factor, and the indirect effect is more significant for adolescents with low self-control than for those with high self-control. These findings extend our understanding of how teacher-student relationships influence academic achievement among adolescents. The results have theoretical and practical value for guiding educational work in schools and improving the academic achievement of adolescents.