Background Marijuana use among adolescents may have increased after its legalization in the United States. An association between violence and marijuana use in adults has been demonstrated in previous reports. We hypothesized that adolescent trauma patients presenting with a positive marijuana screen (pMS) are more likely to have been injured by gunfire or knives and will have more severe injuries overall, compared to patients with a negative marijuana screen (nMS). Methods The 2017 Trauma Quality Improvement Program database was queried for adolescent (13-17 years old) pMS patients and compared to adolescents who tested negative for all substance/alcohol. Patients with positive polysubstance/alcohol were excluded. Results From 8257 adolescent trauma patients, 2060 (24.9%) had a pMS with a higher rate of males in the pMS group (76.3% vs 64.3%, P < .001). The pMS group presented more frequently after gun (20.3% vs 7.9%, P < .001) or knife trauma (5.7% vs 3.0%, P < .001) and less frequently after falls (8.9% vs 15.6%, P < .001) and bicycle collisions (3.3% vs 4.8%, P = .002). The rate of serious thoracic injury (AIS ≥3) was higher for pMS patients (16.7% vs 12.0%, P < .001), and more pMS patients required emergent operation (14.9% vs 10.6%, P < .001). Discussion In our adolescent patient population, one quarter tested positive for marijuana. These patients are more likely to be injured by guns and/or knives suffering serious injuries, and often require immediate operative intervention. A marijuana cessation program for adolescents can help improve outcomes in this high-risk patient group.