Objective: Converging evidence suggests deficits in theory-of-mind (ToM) processing in patients with anorexia nervosa (AN). The present study aimed at elucidating the neural mechanisms underlying ToM-deficits in AN. Method: A total of 19 adolescent patients with AN and 21 age-matched controls were investigated using functional magnetic resonance imaging during performance of a ToM-task at two time points (in-patients: admission to hospital and discharge after weight recovery). Clinical outcomes in patients were determined 1 year after admission. Results: Irrespective of the time point, AN patients showed reduced activation in middle and anterior temporal cortex and in the medial prefrontal cortex. Hypoactivation in the medial prefrontal cortex at admission to hospital (T1) was correlated with clinical outcome at follow-up. Conclusions: Hypoactivation in the brain network supporting theory of mind may be associated with a social-cognitive endophenotype reflecting impairments of social functioning in anorexia nervosa which is predictive for a poor outcome at 1-year follow-up. (Contains 6 tables, 6 figures, and 3 videos.)