Chapter 22 in 'The Wiley Handbook on What Works with Girls and Women in Conflict with the Law: A Critical Review of Theory, Practice, and Policy'. This chapter discusses the nature and scope of mental health problems among justice-involved females with a focus on internalizing mental disorders. It summarizes the literature into trauma history and mental illness as explanatory factors for offending behavior in females, followed by a discussion of internalizing mental disorders, more specifically post traumatic stress disorder, anxiety, and depressive disorders, and on related symptomatology like self-injury behaviors. The relationship between trauma history and offending is mediated by mental health problems. The chapter provides several clinical case examples to illustrate the role serious mental health problems may have in violent offending behavior and the often complex needs of justice-involved females with mental health problems. It presents some recommendations regarding assessment and treatment responsive to gender differences for practitioners in the forensic field. Both justice-involved females and males who enter prison treatment programs or forensic mental health services have complex backgrounds with high rates of victimization and complex psychiatric problems.