BackgroundWomen who have experienced domestic violence and abuse (DVA) are at increased risk of developing post-traumatic stress disorder (PTSD) and complex PTSD (CPTSD). In 2014–2015, we developed a prototype trauma-specific mindfulness-based cognitive therapy curriculum (TS-MBCT) for the treatment of PTSD in a DVA population. This study aimed to refine the prototype TS-MBCT and evaluate the feasibility of conducting a randomised controlled trial (RCT) testing its effectiveness and cost-effectiveness.MethodsIntervention refinement phase was informed by evidence synthesis from a literature review, qualitative interviews with professionals and DVA survivors, and a consensus exercise with experts in trauma and mindfulness. We tested the refined TS-MBCT intervention in an individually randomised parallel group feasibility trial with pre-specified progression criteria, a traffic light system, and embedded process and health economics evaluations.ResultsThe TS-MBCT intervention consisted of eight group sessions and home practice. We screened 109 women in a DVA agency and recruited 20 (15 TS-MBCT, 5 self-referral to National Health Service (NHS) psychological treatment), with 80% follow-up at 6 months. Our TS-MBCT intervention had 73% uptake, 100% retention, and high acceptability. Participants suggested recruitment via multiple agencies, and additional safety measures. Randomisation into the NHS control arm did not work due to long waiting lists and previous negative experiences. Three self-administered PTSD/CPTSD questionnaires produced differing outcomes thus a clinician administered measure might work better. We met six out of nine feasibility progression criteria at green and three at amber targets demonstrating that it is possible to conduct a full-size RCT of the TS-MBCT intervention after making minor amendments to recruitment and randomisation procedures, the control intervention, primary outcomes measures, and intervention content. At 6 months, none of the PTSD/CPTSD outcomes ruled out a clinically important difference between trial arms indicating that it is reasonable to proceed to a full-size RCT to estimate these outcomes with greater precision.ConclusionsA future RCT of the coMforT TS-MBCT intervention should have an internal pilot, recruit from multiple DVA agencies, NHS and non-NHS settings, have an active control psychological treatment, use robust randomisation and safety procedures, and clinician-administered measures for PTSD/CPTSD.Trial registrationISRCTN6445806511/01/2019.Supplementary InformationThe online version contains supplementary material available at 10.1186/s40814-023-01335-w.