The research apprenticeship is a situated form of learning that can be effective in connecting learners to science. It is commonly assumed that this pathway is characterised by power transitions from those positioned as experts to those positioned as novices, yet power and positionality during a research apprenticeship have rarely been explicitly investigated. Using a qualitative approach, we explored this area in the context of a summer research apprenticeship for girls, involving primarily female scientist mentors. We found that scientist mentors positioned, and were positioned by, learners in three different ways, and that these positionalities were associated with different kinds of identity work among learners. Given stereotypical societal views of science that can be at odds with gendered identities, these patterns may be particularly consequential for girls. We discuss implications for teacher professional development, as well as future research directions.