Latent profile analysis (LPA) was used to classify 394 adolescents undergoing substance use treatment, based on past year psychiatric symptoms. Relations between profile membership and (a) self-reported childhood maltreatment experiences and (b) current sexual risk behavior were examined. LPA generated three psychiatric symptom profiles: Low-, High- Alcohol-, and High- Internalizing Symptoms profiles. Analyses identified significant associations between profile membership and childhood sexual abuse and emotional neglect ratings, as well as co-occurring sex with substance use and unprotected intercourse. Profiles with elevated psychiatric symptom scores (e.g., internalizing problems, alcohol abuse and dependence symptoms) and more severe maltreatment histories reported higher scores for behavioral risk factors for HIV/STI exposure. Heterogeneity in psychiatric symptom patterns among youth receiving substance use treatment services, and prior histories of childhood maltreatment, have significant implications for the design and delivery of HIV/STI prevention programs to this population.