Objectives: We explored mothers' and clinicians' experiences of a video feedback intervention adapted for perinatal 'personality disorder' (VIPP-PMH) and the acceptability of a randomised controlled trial (RCT) examining its effectiveness. Design: In-depth qualitative interviews with participants from a two-phase feasibility study of the VIPP-PMH intervention. Participants were mothers experiencing enduring difficulties in managing emotions and relationships, consistent with a 'personality disorder', and their 6-to 36-month-old children. Methods: Forty-four qualitative interviews were conducted, including all nine mothers receiving VIPP-PMH during the pilot phase, 25 of the 34 mothers participating in the RCT (14 allocated to the VIPP-PMH arm and 9 from the control arm), 11 of the 12 clinicians delivering VIPP-PMH and one researcher. Interview data were thematically analysed. Results: Mothers described feeling motivated to take part in the research and understood the need for randomisation. Research visits were largely experienced positively, with some suggestions for improvement in questionnaire timing and accessibility. Almost all mothers initially felt anxious about being filmed, but reported positive experiences of the intervention, particularly valuing its non-judgemental, positive and child-focussed nature, their supportive relationship with the therapist and the insights they gained on their child.