Background: The occurrence of attenuated psychotic symptoms (APS) is a major concern in populations with substance use disorders (SUDs). However, APS also frequently develop in the course of Post-Traumatic Stress Disorder (PTSD). This study explores how the prevalence of APS differs between adolescent patients with only SUD, SUD with a history of traumatic experiences (TEs), and with SUD and self-reported PTSD. Methods: We recruited n = 120 treatment-seeking adolescents at a German outpatient clinic for adolescents with SUD. All participants filled out questionnaires assessing APS (PQ-16, YSR schizoid scale), trauma history, PTSD symptoms (both UCLA PTSD Index), and SUD severity (DUDIT) next to an extensive substance use interview. We performed a multivariate analysis of co-variance with the four PQ-16 scales and the YSR scale as outcomes and PTSD status as predictor. Additionally, we performed five linear regressions predicting each PQ-16 score and YSR score based on tobacco, alcohol, cannabis, ecstasy, amphetamine, and methamphetamine use. Results: Participants with co-occurring SUD and self-reported PTSD showed significantly higher APS prevalence rates (PQ-16 score, p =.00002), more disturbed thought content (p =.000004), more perceptual disturbances (p =.002), more negative symptoms (p =.004) and more thought problems (p =.001) compared to adolescents with SUD and a history of trauma and adolescents with only SUD. Past-year substance use was not predictive for APS prevalence (F(75) = 0.42; p =.86; R ² =.04). Conclusion: Our data suggests that the occurrence of APS in adolescents with SUD is better explained by co-occurring self-reported PTSD than by substance use frequency or substance class. This finding might indicate that APS might be reduced through treating PTSD or focusing on TEs in SUD therapy.