Summary Background The pattern of endocrine disorders in long-term survivors of childhood cancer has not been investigated comprehensively. Here, we aimed to assess the lifetime risk of these disorders in Nordic survivors of childhood cancer. Methods From the national cancer registries of Denmark, Finland, Iceland, Norway, and Sweden, we identified 31 723 1-year survivors of childhood cancer, notified since the start of registration in the 1940s and 1950s. From the national population registries, we randomly selected a comparison cohort of people matched by age, sex, and country. Study participants were linked to the national hospital registries, and observed numbers of first-time hospital contacts for endocrine disorders in survivors of childhood cancer were compared with the expected numbers derived from the population comparison cohort. We calculated the absolute excess risks attributable to status as a childhood cancer survivor and standardised hospitalisation rate ratios (SHRRs). Findings Of the childhood cancer survivors, 3292 had contact with a hospital for an endocrine disorder, yielding a SHRR of 4·8 (95% CI 4·6–5·0); the highest risks were in survivors of leukaemia (SHRR 7·3 95% CI 6·7–7·9), CNS tumours (6·6 6·2–7·0), and Hodgkin's lymphoma (6·2 5·6–7·0). The absolute excess risk for endocrine disorders was roughly 1000 per 100 000 person-years before 20 years of age, and 400 per 100 000 person-years during the remaining lifetime. For children with cancer diagnosed at 5–9 years of age, the cumulative risk for endocrine disorders was highest, and reached 43% at the age of 60 years. Diagnoses of pituitary hypofunction (SHRR 88·0), hypothyroidism (9·9), and testicular and ovarian dysfunction (42·5 and 4·7, respectively) together constituted 61% (655 of 1078) of all excess disease-induced and treatment-induced endocrine disorders in survivors of childhood cancer. Interpretation A cumulative risk for endocrine disorders at 60 years of age of above 40% in survivors of childhood cancer emphasises the importance of minimisation of damaging treatment, intensification of secondary prevention, and targeting of survivor follow-up throughout life. Since most long-term childhood cancer survivors are not followed in a specialised late-effect clinic, they are a growing challenge for the primary care physician and medical specialists working outside the late-effect area. Funding The Danish Council for Strategic Research.