IMPORTANCEMajor depression and substance use disorders (SUD) commonly co-occur among adolescents, yet little is known about treatment use among adolescents with both conditions. Given the reciprocal influence of these conditions on each other and low prevalence of treatment overall, current information on quantification and trends in treatment of co-occurring depression and SUD is critical toward assessing how the field is performing in reaching youth in need of these services, and among youth with sociodemographic risk factors. OBJECTIVE To examine temporal trends and sociodemographic disparities in the treatment of co-occurring major depression and SUD among US adolescents. DESIGN, SETTING, AND PARTICIPANTS This survey study used publicly available data for adolescents aged 12 to 17 years from the annual cross-sectional surveys of the National Survey on Drug Use and Health from 2011 to 2019 to assess co-occurrence of major depressive episodes (MDE) and SUD through time and prevalence of treatment for either or both of these conditions. Data were analyzed between October 2020 and February 2021. EXPOSURES Survey years, adolescent age, gender, race and ethnicity, type of insurance, annual household income, family structure, and residential stability. MAIN OUTCOMES AND MEASURES Presence and treatment of co-occurring 12-month MDE and SUD.