Adolescent gang members are at high risk for polytraumatization (i.e., experiencing two or more types of trauma), which may contribute to behavioral problems, such as delinquency or drug distribution, and mental health symptoms, such as posttraumatic stress disorder (PTSD) and depression. The present study examined the associations between polytraumatization and these behavioral and mental health outcomes. We hypothesized that increased polytraumatization would lead to increased (b) mental health symptoms, (b) delinquency, and (c) drug distribution. Participants included 441 adolescent gang members (57.8% male; age range: 14–19 years) from a midsized city in the Midwestern United States. A path model was used to test hypotheses. A total of 88.0% of participants experienced polytraumatization, such as physical and sexual assault, involvement in accidents, or witnessing a death or injury. Polytraumatization was uniquely and positively associated with depressive and PTSD symptoms, delinquency, and drug distribution, βs = .25–.50, ps < .001, explaining an additional 5.9%–22.5% of the variance in these outcomes beyond covariates. Untreated traumatic exposure among adolescent gang members may subsequently lead to poor behavioral and mental health outcomes. These results may inform prevention and intervention efforts focused on mental health and social justice among a high‐risk adolescent population.