Massive Open Online Courses (MOOCs) are used by many educators for professional development (PD). However, only a few studies explored what educators’ goals in PD-MOOCs are and whether educators with different goals interact with MOOCs in different ways. These issues are addressed in three related studies described in this work. First, I conducted a literature review on MOOCs for educators and identified underexplored topics and underutilized data collection and analysis methods. I found that a few studies looked at educators’ learning motivations and none linked them to complex engagement patterns as measured using log data. In the second study, I used natural language processing (NLP) to identify teachers’ motivations in four MOOCs (n = 3,212) based on their responses to open-ended and Likert-style survey items. I also examined the association between these motivations, participants’ intention to complete the course, and actual completion. Three motivation groups were identified: Intrinsic, Professional, and Prosocial (i.e., taking the course to help students or improve the educational system). Participants with intrinsic motivations were less likely and those with prosocial motivations were more likely to plan to complete the course or to complete it even after accounting for initial intentions. In the third study, I compared the engagement processes of the three motivation groups in one course (n = 969). I found that the intrinsic motivation group was the most engaged during the course, but the prosocial group was the most engaged by its end. The prosocial participants were also the most interested in the course’s forum. These findings have theoretical and practical implications for the study of MOOCs and educators’ PD in general. They can, for example, be used to enhance PD design in a way that helps educators meet their individual goals. Rethinking the design of educators’ PD courses this way can potentially affect their teaching practice and thus, improve education for their students, as well.