Online professional-development courses such as massive open online courses (MOOCs) could bring relevant content to a wider base of teachers who might not otherwise have access to professional development. However, research on the relevance of such online courses is scarce. The main aim of this study is to investigate the relevance (individual, societal, and vocational) of MOOCs (mostly participatory cMOOCs) from the viewpoint of teachers now and in the future. We examined teachers' expectations and perceptions of 10 courses before (N = 364) and after (N = 177) the courses, using an online questionnaire developed on the basis of relevance theory. According to the results, the studied teachers had positive expectations for the courses in terms of their usefulness for their prospective teaching (especially vocational relevance). Teachers' expectations related to the usefulness of the course for the future (individual and vocational relevance) were most strongly met. Effort put into the course was connected to, for example, how the course improved the teachers' interest. The results of this study indicate that MOOCs can serve as relevant courses for teachers' professional development in science, mathematics, and technology education.