In a 25-year Australian cohort of men and women found Not Guilty by reason of Mental Illness (NGMI forensic patients; N = 477), we aimed to: establish the sociodemographic, clinical and forensic characteristics of the sample, comparing men and women; to establish rates of post-release reoffending, including for men and women separately; and to test associations between individual characteristics and post-release re-offending in the full sample. Post-release re-offending was considered in terms of officially-recorded charges, proven offenses, violent offenses, and any offending within the first 12 months of release. Women (13.8%) were found to differ significantly from men on a number of key characteristics but, although women had a higher rate of proven offending in the early post-release period, sex was not a predictor of post-release offending overall. Post-release re-offending rates were low (6.3% committed proven offenses in the first 12 months following release) and the only independent predictor of re-offending was a clinically-recorded diagnosis of co-morbid personality disorder (i.e. co-morbid with a primary psychosis diagnosis). The differences identified between male and female NGMI forensic patients, including the differences in re-offending in the early post-release period, have implications for the development of forensic services and interventions, in both inpatient and community settings.