This article provides a narrative review of potential harmful effects of group‐based treatment for adolescent substance use. We first describe potential harms thought to be induced by peer deviancy training and discuss how deviancy training concerns have widely impacted youth intervention science and policy. We next review evidence supporting various group treatment models for adolescent substance use and delineate how providers might inoculate group treatment against deviancy training processes. We then underscore limitations in statistical validity that characterize many deviancy training studies and offer methodological guidelines to advance assessment of harmful effects. We conclude that group‐based intervention is an effective treatment modality for adolescent substance use posing no exceptional risk of iatrogenic effects and suggest innovations to increase its delivery.