Despite the growth of research on EAP teachers in the past decade, little research has focused on their emotions and much less on their well-being. In response to this gap of knowledge, the present study draws on the theoretical framework of activity theory and explores the well-being of 13 Iranian EAP teachers. We collected data from a questionnaire, narrative frames, and semi-structured interviews. Data analyses revealed three themes in relation to the teachers' well-being: (1) content as a site of experiencing positive and negative emotions, (2) content and institutional contextualities as determinants of seeking purpose in EAP instruction, and (3) sociocultural parameters as shaping meaning in EAP instruction. We found that EAP teacher well-being functions as a layered construct that is influenced by various personal, institutional, and sociocultural dynamics, and substantially influences teachers' professional practices, identities, and emotions. Across these processes, content operates as the antecedent or consequence of the influence in EAP instruction. Based on the findings, we provide implications for teachers and teacher educators in how to employ professional alternatives that could effectively contribute to EAP teachers' well-being.