Coaches` behavior is one of the most important factors affecting young players` aggressive actions. Coaches` ignorance toward players` unwanted actions may sometimes perceived as positive feedbacks by players and support their aggressive behaviors. It is possible also that some coaches directly encourage players to accomplish aggressive acts. Therefore, "in what extent young players aggressive actions correspond to coaches` behavior?," is the main question that the present study tries to answer. Accordingly, competitions in 2004 nation high schools championship (including 115 teams, 302 matches, and 1531 players in volleyball, basketball, handball, football, and futsal) were closely observed and players` aggressive and assertive behaviors were recorded. To code and analyze coaches` behavior, the coaching behavior assessment system (CBAS) was used. This instrument classifies coaches` behavior in twelve classes and is widely used in studies related to describing and analyzing coaches` behavior. Results indicated that most players` aggressive acts correlated with several coaches` behaviors, namely ignoring mistakes, reinforcement, keeping control, and mistake-contingent technical instruction. Moreover, it was found that girls committed more instrumental and boys more goal aggressions. The results are discussed in relation to the aggression literature. Investigation of causal relation of these behaviors is recommended.