Currently, a conjunction of policy, legislative change in health and social care and the criminal justice system, combined with funding for innovative services make it opportune to assess the evidence base for interventions with women offenders. Women offenders have a distinctive criminological, health and social profile and a gender specific approach to their difficulties is advocated. This systematic review and meta-analysis focus on mental health gain in adult women offenders in forensic health settings, criminal justice institutions and in the community, following therapeutic interventions. Interventions were assessed in terms of specific outcome measures of depression, trauma symptomatology and global mental health status. Comprehensive search strategies yielded 3018 articles, from which we obtained 199 full text articles. Seventeen articles were included in the final review, of which six were excluded from the meta-analysis as there was no comparator group. There is a modest, but increasing, body of evidence for the utility of some interventions, notably those addressing the consequences of earlier trauma, including interventions which also address comorbid substance misuse. This does not amount, to date, to a robust evidence base. Limitations of these studies are discussed and include small sample sizes, their restriction mainly to prison populations and that they were substantially undertaken in the US. Variations in outcome measures follow-up and the difficulties inherent in measuring change in this complex population are also detailed. However, the review delineates definite avenues for further work. To achieve this, those responsible for policy, practice and purchase of services should both be mindful of existing evidence and promote additional, high quality research into interventions which are designed around a coherent, theoretical approach.