Electronic music dance events (EMDEs) at nightclubs attract young adults engaging in high-risk alcohol and other drug (AOD) use. Studies show that most patrons arrive at clubs in groups and that these peer groups influence drinking. Therefore, peer groups are a natural context for preventing risk behaviors. This article examined outcomes of a randomized controlled trial of a group-based mobile intervention at nightclubs, Nightlife Safety Plans (NSP).The sample comprised 352 groups, consisting of 959 participants (45.3% female) at 41 events across seven nightclubs hosting EMDEs. Club patrons were surveyed anonymously and completed breath tests as they entered and exited clubs. Oral fluid samples collected from patrons at exit assessed drug use. Analyses examining assignment to NSP versus a control condition on fire safety predicted individual- and group-level protective strategy use and AOD use, controlling for background variables.At the individual level, participation in NSP was related to increased protective actions to keep group members safe. No effects were found on actions to keep oneself safe or in response to overuse. At the group level, assignment to NSP was related to a higher average number of group safety strategies. Participation in NSP was associated with lower blood alcohol concentration but unrelated to tetrahydrocannabinol and cocaine.NSP appears to be efficacious for increased protective actions to keep group members safe from overuse and for reduced blood alcohol concentration among EMDE patrons. The findings support the use of an intervention utilizing group-based strategies presented proximal to risk settings.