Objective To determine the efficacy of 10 session body image therapy (BAT‐10) in the treatment of anorexia nervosa with adherence to the methodological guidance for complex interventions. Method Fifty‐five adult inpatients with anorexia nervosa at two national centres received the group‐based manualised body‐image therapy (BAT‐10). BAT‐10 was refined, developed and manualised over two decades, by using the mindfulness‐based cognitive behavioural therapy, including mirror exposure. Outcomes were evaluated using Body Checking Questionnaire, Body Image Avoidance Questionnaire, Physical Appearance State and Trait Anxiety Scale, Eating Disorders Examination Questionnaire and Quality of Life in Eating Disorders. Participant experience was evaluated qualitatively by an interpretative phenomenological analysis. Results Ten session body image therapy achieved highly statistically significant changes in body checking, body avoidance and anxiety, as well as shape‐concern and weight‐concern, without the between‐therapist effects. The quality of life improved globally but not in relation to the psychological subcategory. Discussion Ten session body image therapy delivers behavioural and cognitive improvements in body image in the short‐term, suggesting an effective, feasible and acceptable manual‐based therapy. Copyright © 2013 John Wiley & Sons, Ltd and Eating Disorders Association.