Purpose: This study aims to investigate the levels of the sense of community among students enrolled in online student communities at Anadolu University Open Education System (OES), as well as their motivations for joining these communities and their expectations. Design/methodology/approach: An explanatory sequential design incorporating mixed research methods was employed as the research framework for this study. Quantitative data were collected from 1,065 students enrolled in online student communities during the 2021-2022 academic year, while qualitative data were obtained from 14 students after the survey using an extreme case sampling method. The quantitative data were analyzed using descriptive statistics, independent samples t-tests, one-way analysis of variance tests, correlation analysis and regression analysis. The qualitative data were analyzed using content analysis. Findings: The study results indicate that students enrolled in online student communities generally have higher levels of a sense of community. These levels did not significantly differ based on gender, employment status, entry type to the university, program studied or membership status in more than one community. However, significant differences were observed in terms of age, time spent in communities and meeting attendance. Additionally, students' perceptions of social presence had a significant effect on their sense of community. Originality/value: This study is the first to investigate the sense of community in online student communities at Anadolu University's OES.