High parental expressed emotion (EE), reflected by criticism or emotional over-involvement, has been related to poorer outcome in family-based treatment (FBT) for adolescent anorexia nervosa. This study assessed EE in 89 mothers and 64 fathers at baseline and end of treatment in a randomised trial comparing conjoint FBT to parent-focused FBT (PFT). Compared with conjoint FBT, PFT was associated with a decrease in maternal criticism, regardless of adolescent remission. Furthermore, an increase in maternal criticism was more likely to be observed in conjoint FBT (80%) than PFT (20%, p = 0.001). Adolescents of mothers who demonstrated an increase in EE, or remained high in EE, were less likely to remit compared with adolescents for whom EE decreased or remained low (33% and 0% vs. 43% and 50%, p = 0.03). There were no significant effects for paternal EE. The results highlight the importance of considering EE when implementing FBT for adolescents with anorexia nervosa. Copyright © 2017 John Wiley & Sons, Ltd and Eating Disorders Association.