As the number of online degree programs continues to grow among higher education institutions in the United States, engaging online adult learners to online degree programs is getting more difficult than before. Therefore, this study, situated in a land grant university, investigated the motivational factors that contribute to adult learners' engagement with online graduate degree programs. Based on 190 sets of survey responses, this quantitative study identified four significant motivational factors (intrinsic motivation, short-term extrinsic motivation, long-term extrinsic motivation, and technological willingness) that contributed to their selection of online programs. Gender differences were found to be influential in intrinsic motivation while age differences could affect learners' short- and long-term extrinsic motivations. Discussions further focused on the implications of the findings in engaging online adult learners in order to sustain online degree programs in higher education.