Understanding predictors of adolescent inpatient length of stay (LOS) is important in informing treatment outcomes for this age group. The current literature on adolescent LOS remains limited and has been characterized by methodological limitations. In the study described here, we examined a wide range of predictors for LOS in a psychiatric unit for adolescents (N=285), including severity of disorder (previous hospitalizations, self-harm, cognitive impairment and thought disorder, severe depression, history of trauma), types of psychotropic medication, and diagnoses. Our results indicated that LOS is associated with predictors that reflect psychiatric severity-most notably prescription of mood stabilizers and youth-reported internalizing symptoms.