Researchers have been interested in the topic of aggression in sports, and research shows it may not only hinder team success but also cause serious injuries (e.g., career-ending injuries) to athletes. Previous studies found that variables (e.g., communication, coaches, and efficacy) increased or decreased aggression in athletes; however, no studies have been conducted to investigate a model including these variables and aggression. Therefore, the purpose of this study is to simultaneously examine the relationships among communication, coach–athlete relationship, team efficacy, and aggression in team sports. After 294 collegiate athletes playing in team sports completed the battery of questionnaires, the data were analyzed for descriptive statistics and the structural equation modeling. The bootstrapping method was utilized to test the mediation effects. The results showed that communication was positively related to the coach–athlete relationship and team efficacy. The coach–athlete relationship was positively related to team efficacy which was negatively related to aggression. The bootstrapping results indicated a significant indirect effect from communication to aggression through coach–athlete relationship and team efficacy. The current study suggests that coaches should improve their communication skills to help athletes to have positive perceptions in the relationships with their coaches, to increase team efficacy, and to reduce aggressive behaviors.