The purpose of this study was to develop a scale with which to examine students' self-regulation (SR) in three types of online interaction. Using scale development steps, we constructed the online self-regulation questionnaire (OSRQ), a self-report survey. A total of 799 online students participated in the study. Data from 400 randomly selected participants were used for exploratory factor analysis (EFA), and data of the remaining 399 participants were used for confirmatory factor analysis (CFA). The EFA yielded three factors as hypothesized: SR in interaction between student and content, SR in interaction between student and student and SR in interaction between student and teacher. The CFA demonstrated that the factor structures appearing in the EFA were also observed with different participants. In addition, we found convergent validity in the OSRQ. The study contributes to understanding SR in online learning settings.