Objective This study aimed to describe the role of parent alliance in Family‐Based Treatment (FBT) for adolescents with anorexia nervosa (AN). Differences between parent and child alliance with the therapist, mothers' and fathers' alliance, and their relationship to outcome were examined. Method Independent observers rated audiotapes of early therapy sessions to assess the therapeutic alliance of parents and adolescents with AN in FBT. Outcome was defined using a previously established cut‐point for recovery from AN. Results Mothers' and fathers' alliance scores with the therapist were similar and significantly higher than adolescent alliance scores early in treatment. Combined parent alliance did not predict recovery at the end of treatment. Difference in alliance scores between mothers and fathers, and parents and their child also did not predict recovery at the end of treatment. Conclusions In FBT, parents developed a strong alliance with the therapist early in treatment. These scores were consistent with the focus in FBT on parental management of eating disorder symptoms, as was the fact that alliance between adolescents and therapists was lower. Although parental therapeutic alliance was likely important in FBT, its role in treatment response remains uncertain. Copyright © 2013 John Wiley & Sons, Ltd and Eating Disorders Association.