The transition to consultant practice represents an important transition from the role of trainee to trainer. We used the theoretical framework of Threshold Concepts to better understand this transition by analysing data from a broader qualitative study examining the experience of early career Certified Gynaecological Oncologists (CGOs) in Australia and New Zealand. Semi-structured interviews were conducted with CGOs of <5 years consultant experience. Transcripts were analysed using reflexive thematic analysis, sensitised by the theoretical framework of Threshold Concepts. Seven early career CGOs were interviewed. Analysis resulted in the construction of five main themes related to the trainer role, each demonstrating characteristics of Threshold Concepts: 'Part of becoming and being a consultant'; 'Managing complex work environments and training responsibilities'; 'Optimising near peer relationships'; 'Recency informing evolution of training'; and "'Being responsible and letting go…' - the next transition." The themes offer insights into the areas of the transition to trainer that are troublesome, the impact of negotiating these challenges on professional identity formation, and the strategies used by CGOs to negotiate them. Using the lens of Threshold Concepts, these experiences can be normalised, and supported through efforts to facilitate the development of skills in reflection, feedback, coaching and mentorship.