Academic engagement and teacher support, as two important factors in education, have been largely neglected in the research literature of English as a Foreign Language (EFL) and applied linguistics. Given the facilitative role of positive emotions in learning processes, this study aimed to examine their mediating role in the relationship between teacher support and academic engagement among Iranian EFL learners. The participants were 435 EFL freshmen randomly selected via multi-stage cluster sampling. The data were collected through previously validated measures. The results of structural equation modelling showed that perceived teacher support could directly and positively affect academic engagement. Additionally, positive emotions mediated the relationship between teacher support and academic engagement. Finally, some important implications and suggestions for further research are presented.