["European Journal of Education, Volume 61, Issue 2, June 2026. ", "\nABSTRACT\nThe role of teachers' emotions in professional practices has been highlighted in the literature. Yet, the interpersonal dimension of teachers' emotions and their regulation has received scant attention. To fill this gap, the present study adopted a triangulated approach to explore the role of interpersonal emotion regulation (IER) in EFL teachers' work engagement (WE) and buoyancy. A sequential explanatory mixed‐methods design was employed, combining three scales and interviews to collect data from 331 Chinese EFL teachers. Pearson correlation analysis revealed significant positive correlations among IER, WE, and workplace buoyancy. Further, multiple regression analysis indicated IER predicted 48% of WE variance and 32% of buoyancy variance, respectively. In the qualitative phase, IER contributed to WE by fostering a positive classroom climate, teacher‐student rapport, and collaboration; for buoyancy, it acted through building professional rapport, mitigating negative emotions, and alleviating emotional labour/pressure, with work cognition also playing a role. The findings elucidate IER's mechanism in EFL teachers' professional well‐being and provide implications for enhancing their interpersonal emotional literacy in theory and practice.\n"]