This mixed-methods study examines how fourth-year English majors at Thu Dau Mot University engage in Zalo-based classroom discussions. Using a convergent parallel design, data were collected through a questionnaire (N = 112) and semi-structured interviews (N = 8) to explore behavioral, cognitive, and emotional dimensions of engagement. Findings reveal that Zalo is primarily used for task coordination and passive monitoring, with limited proactive discussion. Students value its functions for planning and language accuracy but perceive discussions as low in intellectual depth. Emotionally, Zalo fosters social connection and comfort in interacting with peers and lecturers but also introduces pressure to keep up and reluctance to express dissent. The study highlights Zalo’s dual role as a facilitator of convenience and a constraint on deeper learning, suggesting the need for intentional instructional design to promote critical thinking and inclusive dialogue.