In low-income and middle-income countries, an excess in treatment failure for children with cancer usually results from misdiagnosis, inadequate access to treatment, death from toxicity, treatment abandonment, and relapse. The My Child Matters programme of the Sanofi Espoir Foundation has funded 55 paediatric cancer projects in low-income and middle-income countries over 10 years. We assessed the impact of the projects in these regions by using baseline assessments that were done in 2006. Based on these data, estimated 5-year survival in 2016 increased by a median of 5·1%, ranging from −1·5% in Venezuela to 17·5% in Ukraine. Of the 26 861 children per year who develop cancer in the ten index countries with My Child Matters projects that were evaluated in 2006, an estimated additional 1343 children can now expect an increase in survival outcome. For example, in Paraguay, a network of paediatric oncology satellite clinics was established and scaled up to a national level and has managed 884 patients since initiation in 2006. Additionally, the African Retinoblastoma Network was scaled up from a demonstration project in Mali to a network of retinoblastoma referral centres in five sub-Saharan African countries, and the African School of Paediatric Oncology has trained 42 physicians and 100 nurses from 16 countries. The My Child Matters programme has catalysed improvements in cancer care and has complemented the efforts of government, civil society, and the private sector to sustain and scale improvements in health care to a national level. Key elements of successful interventions include strong and sustained local leadership, community engagement, international engagement, and capacity building and support from government.