Borup, Graham, West, Archambault, and Spring (2020) theorized that a student's level of engagement in an online course is influenced by course community support and personal community support, with both factors helping a student to achieve a level of engagement that is not possible independently. In other words, an individual student's ability to engage in an online course can be explained by the kinds of community a student finds within a course and their social support from friends, family, and community as they take the class. The purpose of this study is to understand to what extent course community support and personal community support influence learner engagement. Students who have recently completed an online course were surveyed on their level of engagement in the course, experience of the course community of inquiry, and their level of personal social support. The survey responses were used in a stepwise multiple regression analysis to create a model that explains to what extent course community and personal community explain variations in learner engagement. The results are significant in that they help course designers, instructors, and university support staff understand the interaction between course community, personal community, and learner engagement. That understanding could be used to design both online course content and intervention strategies to maximize learner engagement. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]