This study investigated the effects of play fighting on aggressive behaviors. It was hypothesized that the teaching of play fighting during physical education lessons could reduce self-reported aggression in a group of adolescents to a greater extent than playing volleyball (a low physical contact activity). Participants were 210 young adolescents (mean age ¼ 13.27, SD ¼ 0.48 years) from 10 classrooms that were randomly assigned to an 8- lesson play fighting session or to traditional volleyball lessons. They filled in the 12-item short version of the Aggression Questionnaire (AQ-12) pre- and post-interventions. The play fighting group showed a significant reduction in all the four subscales of the AQ-12 (Cohen d ranging from 0.61 to 0.67), ...