Research has substantiated the significance of student engagement in foreign language learning. Student engagement can be affected by contextual and individual factors. Guided by the general motivation framework, this study investigated the effect of teacher support(emotional, instrumental, informational and appraisal support) on student engagement (behavioral, emotional, cognitive and agentic engagement) in foreign language learning and the potential mediating role of L2 grit. Students’ learning outcomes were also examined. The variables were measured with validated instruments among 355 Chinese EFL students. Structural Equation Modelling (SEM) and correlation analysis generated four major findings: (1) teacher support directly and indirectly predicted student engagement; (2) both perseverance of effort (POE) and consistency of interest (COI) mediated the effect of teacher support on student engagement; (3) the mediation effect of POE was stronger than COI; (4) Engagement was positively associated to foreign language achievement. These results support the general motivational framework by Skinner et al. (2009) on the interactive dynamics of Context, Self, Action and Outcomes in learning. The findings highlight the significance of teacher support in shaping students’ action (engagement) and intrapsychic process (L2 grit) in L2 learning. Theoretical and practical implications and new avenues for future studies are discussed.