IntroductionMedical career preferences are influenced by a multitude of factors. Currently several specialties are undergoing recruitment problems; we must develop our understanding of medical career decision-making to ensure the production of an appropriate workforce. We aimed to explore the changing career preferences of students during medical school, to better understand this.MethodsThis was an interpretivist, qualitative study. Data were collected through semi-structured interviews with seven final-year students to explore why their career preferences had changed during medical school. Transcripts of these interviews were thematically analysed.ResultsThree overarching themes emerged from the analysis: The ‘influence of medical school’, ‘perceived suitability to specialty’ and ‘belonging and fitting in’. A thematic map captured the participants’ perceptions on why their preferences had changed, with major influences echoing existing research. However, novel findings included participants’ personalities and enthusiasm changing over time, the need for a ‘sense of belonging’ and participants defining the term ‘variety’ uniquely, perceiving their current specialty preference to match their definition.DiscussionThis was an original, in-depth study on changing career preferences, which is an ill-defined subject within the literature. Analysis revealed preferences changed for a variety of medical school, personal and specialty reasons, leading to the construction of an updated model of medical career decision-making. Medical career preference remains a dynamic and ever-evolving phenomenon, influenced by an intricate interplay of internal and external factors. An understanding of this is crucial for future workforce planning.Electronic supplementary materialThe online version of this article (10.1007/s40037-020-00636-7) contains supplementary material, which is available to authorized users.