The emergence and development of Massive Open Online Courses (MOOCs) has provided access to countless learning resources globally. Although many researchers have investigated the effect of interaction between students’ learning experiences and outcomes, there is still a lack of studies on the factors impacting learner-learner (L-L) interaction and ways to promote L-L interaction in MOOCs. Through a systematic review of relevant articles on L-L interaction in MOOCs, this report synthesizes the factors related to L-L interaction, and methods for improvement, in MOOCs. A total of fourteen peer-reviewed journal articles published in the past ten years were included. The findings indicate that learners’ backgrounds and competencies, course designs, activity levels, and discussion content affected L-L interaction. In addition, methods related to peer-review and discussion can be implemented. The report also proposes some suggestions for course design and future research.