The boundaries between communities of teaching and educational research are very persistent. Boundaries can be conceptualized as sociocultural differences, leading towards discontinuity in action or interaction. Boundary crossing refers to the efforts made to establish continuity. The purpose of this article is to provide a better understanding of how these boundaries can be crossed by teachers who are also PhD students in a national PhD program for educational research in the context of science education. Sixteen teacher researchers as well as their professors and school principals were interviewed. Additionally, two stories were studied of two teacher researchers who seemed successful in crossing boundaries between the two communities. Many differences were found between the two communities, not all of them being boundaries. Specific personal characteristics - such as communication skills and flexible switching – seemed to facilitate boundary crossing, just like particular contextual factors such as school teams with open learning climates and supportive supervisors. All 16 teacher researchers contributed to better science teaching in their own practices, while eight teacher researchers had been able to share insights from their PhD projects with others.