Previous studies have verified that teacher-student relationship quality has a positive effect on students' academic engagement. Few studies, however, have examined whether school psychological capital mediates the linkage between teacher-student relationship and academic engagement. The present study aimed to examine the mediated role of school PsyCap between teacher-student relationship and academic engagement in a sample of 986 Chinese college students in their English as a foreign language (EFL) learning. Having controlled for gender and family resources, structural equation modelling (SEM) analysis was conducted to explore the predictive effect of the teacher-student relationship on academic engagement via mediator of school PsyCap. Results showed that the teacher-student relationship predicted school PsyCap. School PsyCap, in turn, predicted EFL learners' academic engagement. The present study provides evidence for the linkage between teacher-student relationship and academic engagement and contributes to the literature by uncovering the mediator mechanism between these two constructs. Both theoretical and practical implications are discussed.