Background: Although juveniles within the justice system have high psychiatric morbidity, few comprehensive investigations have shown posttraumatic stress disorder (PTSD) in female delinquents. Here, we aim to describe the nature and extent of PTSD and trauma exposure and to clarify the relationships among comorbidity and psychosocial factors in juvenile female offenders. Method: Sixty-four girls were randomly interviewed using structured tools. Self-report measures were used to assess depression, eating behaviour, impulsivity and parental attitude. Results: The PTSD prevalence was 33%, and 77% of the female juvenile offenders had been exposed to trauma. The offenders with PTSD showed a significantly high psychiatric comorbidity. Depression and adverse parenting were associated with PTSD development, and abnormal eating was also correlated with PTSD symptoms. Marked differences in the frequency and intensity of PTSD evaluation depending on the type of comorbidity and trauma were observed. Conclusions: Incarcerated young females in Japan have serious trauma-related problems, and the degree of depression is a strong predictor of PTSD development and symptoms. This study highlights the importance of adequate diagnosis and treatment of PTSD in delinquent female adolescents.