This phenomenological study explored the lived experiences of engagement by non-traditional students in their online courses at a four-year university. The problem addressed by this study was nontraditional students' lack of engagement in their undergraduate online courses at four-year universities. Non-traditional students taking online courses are impacted by this problem. Also, universities that offer online courses and have a high population of nontraditional students are impacted by the problem addressed in this study. The purpose of this phenomenological study was to show the lived experiences of adult students' engagement in their online courses taken at four-year institutions. This study was guided by the online collaborative learning theory (OCL). A qualitative method was used to conduct the phenomenological study. The participants used in this study were nontraditional students who participated in online courses at a four-year university. Data were collected using semi-structured interviews and analyzed using NVivo. The study was guided by three research questions that were designed to understand the participants' shared experiences. The results of the study showed that engagement happened, but not all engagements were the same. The results also show that work and family duties were a barrier to engagement, as was lack of communication between the instructor and classmates, and trouble learning the chosen learning management system. The results showed that multiple technologies were used to promote engagement. As a result of this study, it is recommended that a larger sample be used to conduct further research as well as using a researcher who has no experience taking online courses. This study could be beneficial to universities that offer online courses. These universities can use the results to improve how they structure their online courses. Instructors who are teaching online courses can also use the results of this study to foster better communication with their students. [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/en-US/products/dissertations/individuals.shtml.]