Abstract Background Survivors of childhood cancer may face difficulties at school. We investigated whether childhood cancer affects attainment of upper secondary education, in a register-based cohort study from Denmark, Finland, and Sweden, where we limit bias from selection and participation. Methods From the national cancer registers, we identified all long-term survivors of childhood cancer diagnosed aged 0–14 years in 1971–2005 (n = 7629), compared them to matched population comparisons (n = 35,411) and siblings (n = 6114), using odds ratios (OR) and 95% confidence intervals (CI). Results Overall, 6127 survivors (80%) had attained upper secondary education by age 25, compared to 84% among comparison groups. Elevated OR for not attaining this level were mainly confined to survivors of central nervous system (CNS) tumours (OR_{Surv_PopComp}2.05, 95%CI: 1.83–2.29). Other risk groups were survivors who had spent more time in hospital around cancer diagnosis and those who had hospital contacts in early adulthood, particularly psychiatric. Survivors of all cancer types were less likely to have attained upper secondary education without delay. Conclusions Although survivors of childhood cancer experienced delays in their education, many had caught up by age 25. Except for survivors of CNS tumours, survivors attained upper secondary education to almost the same extent as their peers.