EFL teachers' agency in intercultural teaching is crucial for cultivating foreign language talents with international visions and global competence. Based on the activity theory, the study explores how a school-based professional learning community facilitates EFL teachers' agency in intercultural teaching. Through the collection and analysis of reflection logs, interviews, classroom observations and other data, it was found that the professional learning community's targeted learning activities centered on intercultural elements, cooperative learning atmosphere, and social network support stimulated teachers' motivation to explore intercultural teaching and learning, facilitated them to construct an intercultural teaching knowledge system, and empowered them to carry out intercultural teaching and research. The study not only explores the facilitating factors the school-based professional learning community exerted to promote EFL teachers' agency from the perspective of activity theory, but provides ideas and methodological references for empirical research on EFL teachers' intercultural teaching competence and professional development.