BackgroundMulti-family Therapy (MFT) is being increasingly used in specialist eating disorder services internationally. Despite evidence of its efficacy, little is understood about the treatment mechanisms and what specifically promotes change. This study aimed to understand clinician perspectives on how change occurs during MFT.MethodsClinicians with (a) 5 or more years’ experience facilitating MFT and (b) who had facilitated a minimum of two MFT groups were eligible for this study. Two individual interviews and four semi-structured focus groups were conducted online. Recordings were transcribed verbatim and analysed using reflexive thematic analysis.ResultsTwelve clinicians (five systemic/family psychotherapists, five clinical psychologists, and two consultant child and adolescent psychiatrists) from six different specialist services in the UK participated. Four main inter-connected themes describing how change is perceived to occur were generated; (1) Intensity and immediacy, (2) Flexibility, (3) New ideas and channels of learning and (4) Containment.ConclusionsCurrent data matches closely with young person and parent experiences of MFT and intensive day treatment and how they perceive change to occur. Quantitative data are now needed to evaluate the impact of these factors on outcome.Plain English SummaryMulti-family Therapy (MFT) is being increasingly used in specialist eating disorder services internationally. While there is evidence that it is helpful, little is understood about how the treatment works and what specifically promotes change. This study aimed to understand how clinician believe change to occur during MFT for young people and their family members. Clinicians with (a) five or more years’ experience facilitating MFT and (b) who had facilitated a minimum of two MFT groups were eligible for this study. Two individual interviews and four semi-structured focus groups were conducted online. Recordings were written out word-for-word and analysed using reflexive thematic analysis, a commonly used method for analysing this type of data. Twelve clinicians (five systemic/family psychotherapists, five clinical psychologists, and two consultant child and adolescent psychiatrists) from six different specialist services in the UK participated. Four related themes describing how change is perceived to occur were generated; (1) Intensity and immediacy, (2) Flexibility, (3) New ideas and channels of learning and (4) Containment. Current data matches closely with young person and parent experiences of MFT and intensive day treatment and how they perceive change to occur. These factors now need to be tested in future research.