Objectives Forming part of a process evaluation of a large randomised controlled trial (the Maudsley Outpatient Study of Treatments for Anorexia Nervosa and Related conditions, MOSAIC) comparing two outpatient therapies for Anorexia Nervosa (AN), the Maudsley Model for Treatment of Adults with Anorexia Nervosa (MANTRA) and Specialist Supportive Clinical Management (SSCM), this study adopted a qualitative approach to examine therapist experiences of treatment delivery. Method Twenty MOSAIC therapists completed semi‐structured interviews. Interviews were recorded, transcribed and analysed thematically. Results Themes of positive aspects, challenges and therapeutic fit emerged. MANTRA was seen as structured and flexible but could feel demanding on therapist time and skill. The slow pace and narrower focus of SSCM gave patients space to talk, but the lack of psychological tools and nutritional emphasis could create frustration. Views on the therapeutic relationship and patient‐therapy fit differed across treatments. Discussion Findings provide testable hypotheses about what works for whom, ideas for therapist training, treatment development and delivery. Copyright © 2014 John Wiley & Sons, Ltd and Eating Disorders Association.