Student-to-student connectedness is promoted by active, student-centered learning processes. It is a socio-psychological result of interpersonal communication and behavior in the classroom, which emulates belonging, cohesiveness, and supportiveness among peers. Currently, two survey instruments exist-Dwyer et al.'s (Commun Res Rep 21(3):264-272, 2004. 10.1080/08824090409359988) Connected Classroom Climate Inventory and Johnson's (Commun Res Rep 26(2):146-157, 2009. 10.1080/08824090902861622) amendment thereof, which have been used for nearly two decades to gain insight into instructional processes in face-to-face environments. However, research on student-to-student connectedness is relatively limited in the context of modern, technology-mediated learning environments. Arguably, where student-to-student connectedness is most urgently needed because of the decrease in face-to-face contact time between students and their instructors within online and hybrid learning environments. This study is a systematic literature review that presents a synthesis of twenty-four peer-reviewed journal articles, which empirically investigate student-to-student connectedness within face-to-face, hybrid, and online environments. The documentation of data is organized in accordance to the six aspects of activity theory (subjects, objects, mediating artifacts, rules, community, division of labor) to provide a basis for understanding the dynamics of each research report, as well as to assist identifying the trends and gaps in the literature, thereby expediting future research on this topic.