Despite the accumulating body of knowledge on action research, the scope of research on teacher identity construction in action research is still limited. This study relied on the concept of identities-in-practice and examined four second language (L2) teachers’ identity construction across the plan, act, observe, and reflect stages of action research. Data were collected from semi-structured interviews, reflective journals, and classroom observations. Data analyses indicated that the teachers navigated their action research identity construction through the four stages as: plan (managing the misgivings); act (initial puzzlement, subsequent adaptability, and satisfaction); observe (positive emotions and increased agency); and reflect (further initiatives, greater knowledge generation, and enhanced reflexivity). The study concludes with implications for further empirical attention to the role of emotions in teacher-researchers’ action research engagement and the important role of teacher educators in assisting teacher-researchers with taking the initiative toward conducting action research.