Background: Cancer diagnosis and its treatment may impair the long-term body image of childhood cancer survivors. This may be particularly relevant in adolescence, a critical period of psycho-social development. We compared the body image between adolescent cancer survivors and their siblings, and determined whether survivors’ body image is associated with socio-demographic characteristics, clinical characteristics, and health conditions. Procedure: As part of the nationwide Swiss Childhood Cancer Survivor Study, we sent questionnaires to adolescents (aged 16-19 years), who survived >5 years after having been diagnosed with childhood cancer between 1976-2010. Siblings received the same questionnaire. We assessed the level of agreement with three body image statements referring to body satisfaction and preferences for changes. Chronic health conditions were classified into cardiovascular, pulmonary, endocrine, musculoskeletal, renal/ digestive, neurological, and hearing or vision impairment. We used ordered logistic regression models to identify determinants of a more negative body image. Results: Our study included 504 survivors (48% female) with a median age at study of 17.7 years (IQR 16.8-18.6) and 136 siblings. Survivors and siblings reported overall comparable levels of the three body image statements (all p>0.05). Female survivors (all ORs ≥ 1.7), survivors treated with haematopoietic stem cell transplantation (all ORs ≥ 2.2), and survivors with ≥ 2 chronic health conditions (all ORs ≥ 1.4) reported a more negative body image. This was particularly pronounced for survivors suffering from musculoskeletal or endocrine conditions. Conclusion: Clinicians should address body image concerns in adolescent survivors with chronic conditions and offer psycho-social support if necessary.