•Although increasingly prominent in research ecosystems, principal investigators’ (PIs’) role identity remains ill-defined.•Develop a novel PI role identity learning framework showing the PI role identity is made up of four roles.•Roles are mutually reinforcing throughout the research process and form a hybrid science-business role identity.•Two distinct learning mechanisms – learning through experience and violation – are formative for PI role identity.•PIs, funding bodies and universities must work together to establish role clarity and professional development for PIs. This paper examines the role identity of university based principal investigators (PIs), as well as the learning mechanisms that underpin this position. PIs have become the focus of increasing research attention which has argued that they, along with universities and funding bodies, form an increasingly crucial tripartite in public research environments. Although the PI position is well recognised among scientific peers and research institutions, a role identity is still emerging and remains ill-defined. This issue requires research attention as having a clear role identity is fundamental to performing a role effectively. Our analysis draws on interviews with 41 health science PIs in New Zealand to develop a PI role identity learning framework. We find that the PI role identity is made up of four roles – science networker, research contractor, project manager, and entrepreneur - that are mutually reinforcing throughout the research process, and which together form a hybrid science-business role identity. Furthermore, we identify two learning mechanisms – learning through experience and violation – and show how these are formative for role identity when transitioning to an ill-defined position. Based on our findings we discuss a number of practical implications for PIs, universities and funding bodies.