ABSTRACT Objective To compare psychosocial health and chronic health conditions (CHCs) in bereaved and non‐bereaved adult siblings impacted by childhood cancer and to identify predictors of emotional distress and health‐related quality of life among bereaved siblings. Methods A total of 4558 adult siblings (733 bereaved; 3825 non‐bereaved) of 5‐year survivors of childhood cancer completed measures of emotional distress (Brief Symptom Inventory [BSI]‐18) and health‐related quality of life (Medical Outcomes Survey Short Form [SF]‐36) and reported their social attainment milestones (i.e., educational attainment, employment, and marital status). CHCs’ burden was classified as none/low versus medium/high/very severe. Cancer‐associated complications prior to the patient's death, sibling age at bereavement, and social attainment variables were examined as predictors of emotional distress and health‐related quality of life among bereaved siblings using multivariable modified Poisson regression. Results Bereaved siblings in this sample reported excellent psychosocial health long term (e.g., depressive symptoms 6.5%, somatization 4.4%, anxiety 3.5%). Bereaved siblings had an elevated risk of depression (relative risk [RR] 1.53; 1.10–2.13, p = 0.01), reduced social quality of life (RR 1.35; 1.00–1.82, p = 0.05), diminished educational attainment, and greater CHC burden than non‐bereaved siblings. No differences were observed for other subscales or social attainment outcomes. Among bereaved siblings, risk factors for depression included male sex (RR 0.42; 0.19–0.93, p = 0.05), never being married (RR 3.02; 1.45–6.28, p = 0.05), and greater CHC burden (RR 2.42; 1.18–4.99, p = 0.05). Risk factors for poor social functioning included unemployment (RR 2.24; 1.12–4.45, p = 0.05) and never being married (RR 2.16; 1.22–3.82, p = 0.05). Conclusion Bereaved siblings report excellent psychosocial health long‐term and demonstrate only a marginally elevated risk of experiencing symptoms of depression and poor social quality of life compared to non‐bereaved siblings.