Few studies have examined how the perceived quality of multiple interpersonal relationships is related to eating disorder (ED) symptom severity in adolescents and how psychological variables might influence these associations. The aim of this study is to determine whether the perceived level of trust, communication, and alienation in the relationship with one's mother, father, and peers are predictive of ED severity in adolescent females and to test the mediating effects of low self-esteem and negative mood on these associations. Adolescent females aged 12 to 18 (N = 186) with a diagnosis of Anorexia Nervosa (Restrictive; AN-R or Binge/Purge; AN-B/P) completed self-report measures evaluating the perceived quality of interpersonal relationships, ED symptom severity, low self-esteem, and negative mood. Multiple regressions revealed that the level of perceived alienation in the relationship with one's mother and peers was positively associated with ED symptom severity. Low self-esteem and negative mood acted as mediators of these associations. Considering that a high level of perceived alienation in the relationship with one's mother and peers appears to be associated with more severe ED symptoms through its impact on self-esteem and mood, improvements in the quality of these interactions are likely to be an effective target of intervention among adolescents.