One fifth of all public treatment admissions are emerging adults, and few studies have considered whether treatments are developmentally appropriate. This study compares outcomes between adolescents and emerging adults with substance use disorders who received the Adolescent Community Reinforcement Approach (A-CRA). Propensity score matching was used to create a weighted comparison group of adolescents (n = 151) who had similar demographic characteristics, clinical severity, and treatment retention as the group of emerging adults (n = 152). We examined age differences in abstinence and other psychosocial outcomes at the last available follow-up. Emerging adults and adolescents both reduced their substance use at follow-up. However, emerging adults were less likely to be abstinent and in remission and had more days of alcohol use when compared with adolescents. This study's findings are consistent with prior work on emerging adults. Additional research should examine features of interventions that are most effective in addressing the developmental needs of emerging adults.