Considering the limited attention paid to interpersonal aspects of emotions, this study explored coaches’ perceptions of athletes’ performance-related states and how they used this information for its regulation. Using a case study approach, three coach-athlete dyads from competitive tennis took part in one-on-one semi-structured interviews. Individualized profiling of psychobiosocial states was used to assess athletes’ states in most and least successful performances and as a way of data triangulation. Findings indicated that the coaches paid attention to bodily, motor-behavioural, and operational components of a performance state, and used this information to appropriately adapt their responses to the players’ needs, via the provision of positive reinforcement, and performance-related feedback. The coaches described themselves as calm, patient, and understanding; characteristics that appeared to be vital for the coach-athlete relationship and the coaches’ emotional competence. Findings are discussed within the contexts of emotion regulation and coach-athlete relationship, and how they might be useful to help coaches develop emotional competence.