Despite a substantial body of research exploring diverse aspects of English-medium-instruction (EMI), there is a paucity of research on students’ perceptions of EMI classroom activities and teachers’ instructional language use as English learning affordances, the manifestation of their agency and its mediating factors. Drawing on the ecological concepts of ‘affordance’ and ‘agency’, this inquiry seeks to fill this void using a mixed methods design. One EMI teacher and 134 students in a Chinese university were involved as participants.