Aim: Intensive treatment regimens have contributed to a marked increase in childhood cancer survival rates. Death due to treatment-related adverse effects becomes an increasingly important area to further improve overall survival. In this study, we examined 5-year survival in children with cancer to identify risk factors for treatment-related mortality (TRM). Methods: All children (aged <18 years at diagnosis) diagnosed with cancer in 2 Dutch university hospitals between 2003 and 2013 were included, survival status was determined and causes of death were analysed. Various demographic and treatment factors were evaluated, for which a multivariable competing risks analysis was performed. Results: A total of 1764 patients were included; overall 5-year survival was 78.6%. Of all 378 deaths, 81 (21.4%) were treatment-related, with infection being responsible for more than half of these deaths. Forty percent of TRM occurred in the first three months after initial diagnosis. Factors associated with TRM in the multivariable competing risks analysis were diagnosis of a haematological malignancy, age at diagnosis <1 year and receipt of allogeneic haematopoietic stem cell transplantation. In children suffering from haematological malignancies, TRM accounted for 56.3% of 103 deaths. Conclusion: Over one in five deaths in children with cancer death was related to treatment, mostly due to infection. In children suffering from a haematological malignancy, more children died due to their treatment than due to progression of their disease. To further increase overall survival, clinical and research focus should be placed on lowering TRM rates without compromising anti-tumour efficacy. The findings presented in this study might help identifying areas for improvement