The present study investigates how Content-based Instruction (CBI) fosters multidimensional engagement: emotional, cognitive, and behavioral, among non-English majors at a Chinese tier-2 university. Using a sequential explanatory mixed-methods design, it tracked 200 second-year engineering students across five CBI classes via longitudinal questionnaires. Follow-up semi-structured interviews with five instructors and a focus group with ten students, complemented by classroom observations, provide