This study examined on-field antisocial sports behaviors among 274 American football players in the United States. Results indicated that moral atmosphere (i.e., teammate, coach influence) and conformity to masculine norms were significantly related to participants’ moral behavior on the field (i.e., intimidate, risk injury, cheat, intentionally injure opponents). In other words, the perception that coaches and teammates condone on-field antisocial behaviors—in addition to conforming to societal expectations of traditional masculinity—is related to higher levels of antisocial behaviors on the football field. In addition, conformity to traditional masculine norms mediated the relationship between moral atmosphere and on-field aggressive sports behaviors, suggesting a relationship between social norms and moral atmosphere. Results of this interdisciplinary endeavor are interpreted and situated within the extant literature of both the fields of sport psychology and the psychological study of men and masculinity. Sport psychologists can use results to design interventions that incorporate moral atmosphere and conformity to masculine norms in an effort to decrease aggressive sports behaviors in the violent sport of football.