Epidemiological studies suggest that the incidence of anorexia nervosa (AN) is increasing in younger populations, with some evidence that clinical differences occur according to age of onset (AOO), which may impact prognostic outcomes. The current study sought to compare eating disorder (ED) symptomatology, psychological distress and psychosocial function between early onset (EO), typical onset (TO) and later onset (LO) AN in a large sample of treatment-seeking patients with a diagnosis of AN.