Relatively little is known about the characteristics of female offenders. Here, we studied the prevalence of traumatic brain injury (TBI) and mental health issues in an exclusively female prison population in New Zealand. Participants (N = 38) were recruited from all security levels at Christchurch Women’s Prison. Measures for depression, anxiety, and stress, sleep, and a history of TBI were administered; 94.7% (36/38) of participants presented with a history of TBI. Younger age at first injury was associated with an increased risk of mental health problems. The study concludes that TBI is highly prevalent among female offenders and may be linked to increased mental health problems. TBI should be considered as an important factor in offender pathways and treatment programs.