<p>In an online environment, learners control various factors related to learning. However, a closer examination is necessary to identify the factors that impact their sense of control within online learning. This study aims to explore the factors that constitute learners’ sense of control in online classes and to develop a tool for measuring this construct. To achieve this, we prepared a structured questionnaire to identify the elements that learners believe they can control. Written interviews were conducted with 53 participants via an online platform. Through analysis of the responses, we extracted and categorized the elements that informed the development of a preliminary draft of the measurement tool. After refining and validating the draft, the main survey was conducted with 506 participants. The data were analyzed using content analysis, exploratory factor analysis (EFA), and confirmatory factor analysis (CFA). The findings revealed that learners’ sense of control in online classes could be broadly categorized into two domains: class activities and environment. Within class activities, factors related to course delivery, attitude, and participation were identified, whereas the class environment encompassed factors such as time, space, and media. The measurement tool was developed based on these factors, including specifics such as sequencing, feedback provision, group activities, and device accessibility. Both EFA and CFA were conducted to validate the tool, and the final version was confirmed. This study is significant as it highlights learners’ sense of control as a crucial psychological factor in online learning, which instructors should consider when designing online learning experiences.</p>