Objective Sporting contexts have been found to be both a protective and risk factor in terms of externalising behaviours in adolescence. The current study sought to explain the inconsistent findings by examining the attributes of peers in sporting environments. Specifically, the prosocial and risky attributes of sporting co‐participants were examined as moderators to the relationship between the intensity of sports participation in adolescence and externalising behaviours.

Method Australian adolescents (N = 1,816) were sampled from an economically and geographically diverse range of high schools in Years 9 and 11 (female = 54.7%, Mage = 15.1). The 1,405 sport participants reported on the frequency they engaged in externalising behaviours including minor delinquency and school‐conduct issues. They also reported the proportion of friends in their sport who engaged in prosocial and risky behaviours.

Results The positive association between sports participation intensity and externalising behaviours was moderated by both prosocial and risky peers. More time spent in sport was associated with higher levels of externalising behaviours when the sport exposed the participants to more peers who engaged in risky behaviours and fewer peers who engaged in prosocial behaviours. In contrast, there was no significant association between sports participation intensity and externalising behaviours when the sporting environment included moderate or lower levels of risky peers, irrespective of the level of prosocial peers.

Conclusions This research highlights the need to consider the attributes of co‐participants in structured activities when predicting risks or benefits.