Experiencing sexual trauma has been linked to internalizing and externalizing psychopathologies. Insecure attachment has been shown to moderate the relation between sexual trauma and trauma symptoms among adults. However, few studies have explored relations among sexual trauma, attachment insecurity, and trauma symptoms in adolescence, and none have used developmentally appropriate measures. The present study sought to examine attachment security as a potential moderator of the relation between having a history of sexual trauma (HST) and trauma symptoms among adolescents at an inpatient psychiatric facility. Attachment to caregivers was measured by the Child Attachment Interview (CAI) and trauma symptoms by the Trauma Symptoms Checklist for Children (TSCC). HST was assessed with responses to two separate interviews that asked about traumatic experiences: the Computerized Diagnostic Interview Schedule for Children (C-DISC) and the CAI. Moderation analyses were conducted using univariate General Linear Modeling (GLM). Of the 229 study participants, 50 (21.8%) had a HST. The relation between HST and trauma symptoms was significantly moderated by insecure attachment with both mother, F(1, 228) = 4.818, p = .029, and father, F(1, 228) = 6.370, p = .012. Specifically, insecurely attached adolescents with a HST exhibited trauma symptoms at levels significantly greater than securely attached adolescents with a HST and adolescents with no HST. Results are consistent with previous research that suggests secure attachment may protect against the development of trauma symptoms among those who have experienced a sexual trauma.