Teacher-researcher collaborations inevitably dissolve the border between who is teaching and who is researching, which in turn pushes discussions on research ethics as well as how to define, measure and ensure research validity. In an attempt to deepen the discussion on validity and ethical issues in teacher-research collaboration in science education research, this proposal seeks to disentangle how the notion of ‘ownership’ is transformed in various forms of teacher-researcher collaborations. The paper builds on data from three recent research projects in science education, representing different forms of teacher-researcher collaborations. The analysis focuses how the teachers’ and researchers’ ownership is played out in four stages of the research process; problem stating, design and implementation, analysis, and dissemination. The results indicate that ownership becomes actualised and altered in different ways, and at different stages, depending on the form of collaboration. A conclusion is that ownership needs to be accounted for in in all stages in the research process in order for science education research to accomplish deep relevance and justified implications. Since the question of ownership appears to be particularly troublesome in the last stages of the research process, a suggestion for future teacher-researcher collaboration is to plan for the project’s end, for example in terms of the participants’ anonymity and time to take part in analysis and dissemination of the results, already at the beginning.