Narcissism has emerged as a highly relevant personality trait in sporting contexts, as its competitive environment offers individuals numerous opportunities to pursue personal glory. However, little is known about narcissism in the context of the coach–athlete relationship, and the extent to which similarity in narcissism across coaches and athletes can influence relationship quality. This study sought to explore how similarity in narcissism affects a coach’s perception of their coach–athlete relationship. Data from semistructured interviews with 30 national and international coaches were analyzed using thematic analysis within a critical realist approach. Coaches were purposefully sampled based on their Coach–Athlete Relationship Questionnaire and Dark Triad Dirty Dozen narcissism scores from Stanford et al. (2024). Four groups were then established: similar in trait narcissism/high relationship quality, similar in trait narcissism/low relationship quality, dissimilar in trait narcissism/high relationship quality and dissimilar in trait narcissism/low relationship quality, prior to any interviews. Using Wiltshire and Ronkainen’s (2021) three-level framework of analysis, 70 experiential, 18 inferential, and five dispositional themes were generated. The dispositional themes were perceived relationship perfection, high (perceived) self-awareness, breeding behaviors, relationship power, and relationship elasticity. This study offers an insight into the experiences of similarity in narcissism and the subsequent influence on the quality of the coach–athlete relationship.