Background: Pediatric bipolar disorder (PBD) is associated with psychosocial impairment, but few studies have examined peer relationship functioning and PBD. Adolescence is a crucial developmental period when peers become increasingly salient. Objective: This study compared perceived friendship quality and peer victimization in adolescents with PBD to external community benchmarks and to adolescents with other psychopathology. We also measured the association between peer difficulties and current mood symptoms across diagnoses. Methods: Participants were 189 adolescents, ages 10-17 years (46% female; 58% African American, 32% Caucasian, 10% Other), recruited from a community mental health center (n = 73) and an academic medical center (n = 116). Diagnoses were made via semi-structured diagnostic interviews. Adolescents completed questionnaires to assess peer relationship functioning and mood symptoms. Caregivers completed a questionnaire to assess adolescents' mood symptoms. Results: Adolescents with PBD reported significantly fewer positive and negative qualities in a close friendship and more relational victimization than external community controls. There were no significant differences between adolescents with PBD and those with other psychopathology. Depression and (hypo)mania were both associated with more negative friendship quality and peer victimization. Conclusions: Adolescents with psychiatric disorders reported more peer difficulties than an external community sample, but difficulties were not specific to PBD. Mood symptoms were problematic for perceived close friendship quality and peer victimization in youth with a variety of psychiatric diagnoses. Results suggest that treatments targeting mood symptoms may improve peer relationships and those with an interpersonal focus may be particularly helpful to address mood symptoms.