The aim of this study was to examine longitudinal professional development in distinct types of UK psychologists. We interviewed 9 trainee clinical psychologists (TCPs), and 9 sport and exercise psychologists’ (TSEPs) 3 times at a minimum of yearly intervals during their 3-year (TCP) or 2-year (TSEP) training programme. Participants were registered on either the British Psychological Society (BPS) Qualification in Sport and Exercise Psychology (QSEP; Stage 2), or a doctorate in clinical psychology. We applied a reflexive thematic analysis to transcripts based on a counsellor development framework. Our findings indicate that diverse types of trainee psychologists experience similar patterns of development. Participants: (a) were developing their practice consistent with their personality; (b) experienced changes in emotions and presence during training; and (c) internal developmental processes were influenced by external sources (supervisors, and peers). Findings may help us to understand how trainees fuse their personal and professional selves during training.