Objectives: Adolescent mothers have differing risks and responsibilities compared to adolescent women without children that may impact substance use treatment. This study sought to describe characteristics of adolescent women in a substance use treatment program and determine the effect of adolescent motherhood on treatment program outcomes. Methods: Data were collected from standardized interviews of female adolescents in a case management criminal justice diversion program for substance-using adolescents and adults. Variables included sociodemographic factors (ie, race/ethnicity, age, financial support, education, insurance, marital status, sexual abuse), Diagnostic and Statistical Manual-IV (DSM-IV) substance use disorder diagnoses, and motherhood (ie, childbirth and residence with a child). Treatment program outcome was documented by case workers at the end of the participants' time in the program. Chi-square analyses and analysis of variances determined associations between variables. Logistic regression was used to assess characteristics associated with negative treatment program outcome. Results: Data from 1080 adolescent women aged 16-21 years (mean 19.7 years, SD=1.16) were analyzed; 403 (37%) were mothers. After controlling for sociodemographic factors and substance use disorder diagnoses, adolescent mothers were less likely to successfully complete the treatment program than nonmothers. Adolescent women with reliance on family or friends for financial support, lower education status, and cannabis and cocaine use disorders had worse treatment program outcomes. Conclusions: Childbirth and parenting adversely affect substance use treatment outcomes for adolescent women in the criminal justice system. Future research should explore tailored substance use treatments for adolescents with children. Job training and educational support may improve outcomes.