Despite the potential benefits of action research, teaching action research in a university setting can present challenges. Analyzing my own experiences of teaching a university-based course on action research, this self-study investigates what my students (all classroom teachers) did and did not understand about action research and what hindered them from understanding action research. Data were collected over four semesters by analyzing my course materials, my teaching notes, students' work, and students' email messages. Analysis of the data produced three themes: (1) the uniqueness of teacher culture; (2) teachers' assumptions about teaching and learning; and (3) the epistemological ambiguity of action research. The article offers suggestions for how teacher educators can help teachers better understand the concept of action research and help them to design and carry out meaningful action research projects.