Objective: This study examines the structural relationships between perceived teacher support, academic self-efficacy, and learning engagement among Chinese high school students. It also verifies the mediating effect of academic self-efficacy. Methods: A survey targeting Chinese high school students was conducted; of 580 total responses, 519 valid responses were analyzed. Perceived teacher support, academic self-efficacy, and learning engagement were measured on scales derived from the literature. The collected data were analyzed using SPSS 26.0, AMOS 24.0, descriptive statistics, correlation analysis, and structural equation modeling. Bootstrapping was used to verify the mediating effect. Results: Perceived teacher support was positively correlated with academic self-efficacy and learning engagement, while academic self-efficacy was positively correlated with learning engagement. Both relationships reached significance. A partial mediating effect of academic self-efficacy was also identified in the relationship between perceived teacher support and learning engagement. Conclusions: This study empirically confirms the positive effect of perceived teacher support on high school students’ academic self-efficacy and learning engagement, and that academic self-efficacy plays a significant mediating role in this relationship. The study discusses the educational implications and scope for future research based on these findings.