The internationalisation of higher education (HE) worldwide has led to an expansion of courses using English-as-a-medium-of-instruction (EMI) in non-native-English-speaking countries. Research has identified complex challenges facing EMI educators in implementing EMI policies and suggested separately the significant roles educators' agency and perceptions of EMI play on their EMI practice. However, little is known about how individual educators exercise agency in response to the perceived demands of EMI teaching and the role of their interpretations and perceptions of EMI in the process. Adopting a cultural-historical theory perspective, this study explores how Chinese educators exercise agency to respond to perceived demands of EMI practice. Data included questionnaires and written interviews with ten academics teaching in EMI courses at three Chinese universities. Manifest in their engagement and commitment, deliberate actions and responsibilities towards themselves and students, their agency is unfolded in acts to improve their pedagogy and student learning of academic content, but no/t necessarily to develop students' English proficiency. Educators' perceptions of EMI appear to play a vital role in orienting their agency as they respond to demands from EMI practice when enacting EMI policies.