While research on language teachers' engagement in action research (AR) has received a surge of attention, the influence of AR programs on English language teacher agency remains underexamined. This qualitative study explored how ten English language teachers' perceptions of their agency changed as they participated in an action research engagement program (AREP). Data were collected using semi-structured interviews and reflective journals. The findings revealed that participation in the AR program changed the teachers' perceptions of their agency and empowered them to enact higher levels of agency in their classroom practice. The study also highlights the important role of institutional support in encouraging teachers to engage in the AREP and develop their sense of agency. It also proposes implications for educational managers, teacher educators, and supervisors to help teachers develop higher levels of teacher-researcher agency by providing opportunities to foster engagement in the AREP.