Educators' work is a key element in museums' learning experience, yet knowledge about their professional development is still limited. In this study, we followed three science museum educators' professional growth during collaboration with researchers, with special focus on the introduction of research-based frameworks in their practice. To analyse the dynamics of educators' changes in knowledge, practices, and beliefs, we used the interconnected model of professional growth (Clarke & Hollingsworth, 2002. Teach Teacher Edu, 18, 947-967). During the collaboration, key educators' changes were evidenced in a progressive acquisition of the concepts and ideas and their transformation in functional tools for museum practice. However, the anticipation of potential benefits of the use of the theoretical frameworks, as well as the close collaboration in dialogue between researchers and educators, were pivotal for the development of these changes. Furthermore, our results show the significance of the contextualization of the frameworks in familiar practices, exhibits, and specific science content to use the theory in new contexts. Overall, our results suggest that introducing research-based frameworks in the work of museum educators was a successful approach in the collaboration but, at least to some extent, challenge the use of learning theories as solely ground for professional development in informal settings. K E Y W O R D S practical epistemology analysis, praxeology, professional development Science Education. 2019;103:389-417.wileyonlinelibrary.com/journal/sce