Background The over-representation of female prisoners with borderline personality disorder (BPD) is an area of concern for HM Prison Service. Pilot programmes of Dialectical Behaviour Therapy (DBT) were undertaken for the first time in three British prisons for women diagnosed with BPD. Standard year-long programmes were piloted in two closed training prisons. Three short format programmes were undertaken in a local allocation prison. Method Evaluation measures included psychometric tests, behavioural data, and interviews with participants and key personnel. Sixteen of the 30 women that embarked on the programmes completed them, though five drop-outs were transferred or released, leaving a voluntary attrition rate of 33%. Fourteen completed all measures. A waiting-list control group of eight participants was also set up. Five completed all measures. Results The vast majority of completers showed overall improvements in psychometric data often reaching statistical significance, and with notable effect sizes, while there was no significant overall change in the control group (though improvements were seen). A downturn in overall self-harm was also seen. Conclusion Results are tentative at this stage because of the small sample size. However, despite the numerous challenges associated with implementation, outcomes showed real promise for delivering DBT in a prison setting, its efficacy in reducing criminogenic risk, and improving the manageability and quality of life for this highly problematic group. Lessons learnt for future implementation in correctional settings are discussed.