This study examined the relationships between athletes’ perceptions of coaching effectiveness, based on the coaching efficacy model, and their effort, commitment, enjoyment, self-efficacy, and prosocial and antisocial behavior in rugby union. Participants were 166 adult male rugby-union players (M age = 26.5, SD = 8.5 years), who completed questionnaires measuring their perceptions of four dimensions of coaching effectiveness as well as their effort, commitment, enjoyment, self-efficacy, and prosocial and antisocial behavior. Regression analyses, controlling for rugby experience, revealed that athletes’ perceptions of motivation effectiveness predicted effort, commitment, and enjoyment. Further, perceptions of technique effectiveness predicted self-efficacy, while perceptions of characterbuilding effectiveness predicted prosocial behavior. None of the perceived coaching effectiveness dimensions were related to antisocial behavior. In conclusion, athletes’ evaluations of their coach’s ability to motivate, provide instruction, and instill an attitude of fair play in his athletes have important implications for the variables measured in this study.