This research is situated in the context of English Medium Instruction (EMI) teaching in higher education. The importance of lecturers' skilled implementation of engagement strategies to enhance students' learning is acknowledged. However, literature identifies a need for theoretically informed professional development (PD) programs to improve EMI lecturers' pedagogical engagement. In light of the identified concerns and issues, an intervention, drawing on a pedagogical engagement framework informed by positive psychology, was implemented and reported in this paper. The intention of the study was to contribute to the development of Chinese EMI lecturers' engagement portfolios. A group of twenty-five EMI lecturers in a South China university participated in the study. Through analysing their pre- and post-intervention teaching data and a focus group discussion, it was found that the quality of their cognitive engagement, and the quality of their emotional and behavioral engagement episodes in practice were noticeably improved. It can be concluded that an intensive intervention through a theoretically informed engagement framework contributes to EMI lecturers' pedagogical commitment to students' cognitive learning, and psychological investment in learners’ well-being. However, cultural and institutional factors somewhat constrained the participants from fully embracing the workshops, impacting their perception and post-intervention practice.