The present study investigates the emotional experiences of seven student teachers through the process of lesson study in a pre-service language teacher education course at a university in Macau. Drawing on data from semi-structured interviews, individual reflections, and observational notes, the study reveals a variety of emotions experienced by the participants at different stages of the lesson study, including group lesson planning, micro-teaching, and collaborative and individual reflections. These different emotions served as a rich source of agency and activism for the student teachers, who developed both cognitively and emotionally in this process. In light of these findings, the paper calls for teacher educators to incorporate lesson study as a cognitively and emotionally contested site for pre-service teachers' professional learning. Different emotions and their regulation strategies should be considered for open discussion and explicit instruction in second language teacher education programmes. Research attention should be especially directed towards emotional dissonance among different participants (e.g., student teachers and teacher educators) in teacher education programmes.