Traumatic experiences have been differentiated as interpersonal (i.e., the direct result of actions by other people) or noninterpersonal (i.e., other life‐threatening events, such as severe accidents). Interpersonal trauma exposure generally has been shown to be associated with more severe posttraumatic stress disorder (PTSD) symptoms than noninterpersonal trauma exposure. Interpersonal problems also tend to be associated with trauma exposure and PTSD symptoms, but it is unclear whether a mediating association exists between trauma type, interpersonal problems, and PTSD symptoms. A clinical sample of 4,275 adolescents (age range: 12–18 years) from the National Child Traumatic Stress Network Core Data Set were classified as having experienced interpersonal trauma, noninterpersonal trauma, or both. Interpersonal problems were operationalized by social problem behaviors (e.g., immature and dependent behaviors) and aggressive behaviors on the Child Behavior Checklist. The results of path analyses showed that cumulative interpersonal trauma exposure was both directly and indirectly associated with PTSD symptoms via social problem behaviors but not aggressive behaviors, total effect β = .20, 95% CI [.17, .23]. In a second model, path analyses showed that cumulative interpersonal trauma exposure was associated directly and indirectly via PTSD symptoms with social problem behaviors, total effect β = .15, 95% CI [.11, .18], and aggressive behaviors, total effect β = .13, 95% CI [.09, .17]. These findings suggest that during adolescence, interpersonal problems play an important role in the association between interpersonal trauma exposure and PTSD symptoms.