This systematic review establishes a comprehensive understanding of research trends and the findings of current studies that focus on small-group communication in post-secondary online courses. The review includes 18 journal articles which are categorised and summarised on the basis of their common themes. This review finds that a majority of the studies focus on understanding or uncovering "learning processes" by conducting content analysis (CA). Further research is suggested to investigate "instructional design or methods" to provide instructors with practical knowledge and ideas to enhance and assist the learning processes. Methodological issues are also discussed, including coding reliability in CA, quantitative measures for assessing collaboration, and a need for causal relational experimental studies.