Teaching in today's changing society requires teachers' independent judgement and development. One way of fostering professional development is action research; described, however, as a challenging and time-consuming process. This qualitative study asks whether action research is worthwhile already in pre-service teacher education, or whether the challenges outweigh the gains. Furthermore, it asks how a teacher educator, here the author of the article, could guide student-teachers' action research projects. The main data source is student-teachers' research reports, which are analysed and reflected upon in light of professional development. The study revealed that action research under certain conditions offers a potential for professional development for student-teachers.