Online learning has become an essential part of acquiring academic and professional qualifications in higher education. Online learning recently gained attention as an effective instructional approach to enhance learning engagement, causing many universities to implement it. To promote learning engagement in online learning environments in higher education, this study collected data from 354 full-time undergraduate students in a large public Chinese university and examined the effects of teacher-student interaction, student-student interaction, and social presence on learning engagement. The research findings indicated that teacher-student and student-student interaction directly affected social presence and learning engagement in online environments. And social presence also directly affected learning engagement. Meanwhile, social presence also mediated the relationship between teacher-student interaction and learning engagement and student-student interaction and learning engagement. This study confirmed the significant effects of teacher-student interaction, student-student and social presence on students' learning engagement in online environments. The findings of this study have significant practical implications for teaching practices.