Athletes' perceptions of coaches' communicative acts of interaction in two key interpersonal situations were examined, and their impact on the athletes: (a) when athletes lose competitions; and, (b) when athletes make mistakes in training. Athletes (N = 324, M age = 20.11) completed an open-ended survey. Data were deductively and inductively analyzed. Athletes perceived coaches' communicative acts to be positive (e.g., performance analysis and feedback) and negative (e.g., hostile reaction), and to impact their motivation, affect, physical self-concept, and learning. The study highlights the salient role of coaches' communication in theses situations and discusses its theoretical and practical implications in the sport performance context. (Contains 2 tables.)