As a key element in teacher education programmes, action research is a learning process in which pre-service teachers inquire, reflect on and improve their teaching practices. This qualitative study sought to understand what enhanced or hindered Thai pre-service teachers' action research projects during their student teaching. This study drew upon written reflections, focus-group interviews and observations of seminar sessions. Data analysis was inductive, involving categorical aggregation followed by a search for correspondence and patterns. The results indicated that the pre-service teachers misunderstood action research, and also held a negative attitude toward it, both of which led them to superficial analyses of practice. They struggled with time limitations, data gathering and interpretation strategies. In spite of the struggles they experienced, these pre-service science teachers did learn more about the action research through collaboratively working with cooperating teachers and university supervisors and on-campus seminar discussions held concurrently with the fifth year internship. Recognizing and understanding the reasons and thinking patterns at the root of these teachers' difficulties with learning about action research can form the basis for reflecting on and rethinking the components of science teacher preparation programmes in Thailand.