<p>This study examines the manifestations and mediating factors of agency for research among four Chinese university foreign language teachers through an activity theory lens. Using a multiple case study approach, data from interviews, journals, documents, and profiles were analyzed via the constant comparative method. Findings reveal teacher agency for research manifests through three interconnected dimensions: agency beliefs, agency practice, and agency disposition. Second, these manifestations of teacher agency for research were mediated by various elements within the research activity system. Specifically, at the subject level, university foreign language teacher agency for research was mediated by research competency and motivational factors. The mediational tools comprised social interactions, cultural artifacts, and activity structures. Object-oriented mediation was evidenced through the enhancement and cultivation of teacher agency for research via evolving objectives across different research activities. Furthermore, the institutional rules, community dynamics, and division of labor collectively constituted the socio-cultural context that mediated teacher agency for research. The study contributes to understanding how EFL teachers navigate dual teaching-research roles in higher education contexts where research productivity is increasingly emphasized and substantively to the existing body of knowledge on teacher agency.</p>