The role of motivation in online learning has been explored mostly as a predictor of course retention or satisfaction, rather than as an adaptive outcome in itself. We thus aimed to investigate how the features of motivation develop in online courses during the semester and how students' perceived teaching and social presences influence their motivational growth in online learning. A total of 152 college students responded to a questionnaire about motivational beliefs, expectancies, and task values, in an online course three times during a semester, as well as perceived teaching and social presences assessed once. Latent growth models reported all motivation variables significantly and positively developed over time, and the motivational growths were predicted by teaching and social presences. More precisely, teaching presence predicted baseline expectancies at the beginning of the course, while social presence predicted both baseline and growth of expectancies and intrinsic value over the course duration.