OBJECTIVE: To estimate how many children and adolescent worldwide do not have access to surgical care. METHODS: We estimated the number of children and adolescents younger than 19 years worldwide without access to safe, affordable and timely surgical care, by using population data for 2017 from the United Nations and international data on surgical access in 2015. We categorized countries by World Bank country income group and obtained the proportion of the population with no access to surgical care from a study by the Lancet Commission on Global Surgery. FINDINGS: An estimated 1.7 billion (95% credible interval: 1.6-1.8) children and adolescents worldwide did not have access to surgical care in 2017. Lack of access occurred overwhelmingly in low- and middle-income countries where children and adolescents make up a disproportionately large fraction of the population. Moreover, 453 million children younger than 5 years did not have access to basic life-saving surgical care. According to Lancet Commission on Global Surgery criteria, less than 3% of the paediatric population in low-income countries and less than 8% in lower-middle-income countries had access to surgical care. CONCLUSION: There were substantial gaps in the availability of surgical services for children worldwide, particularly in low- and middle-income countries. Future research should focus on developing specific measures for assessing paediatric surgical access, delivery and outcomes and on clarifying how limited surgical access in the poorest parts of the world affects child health, especially mortality in children younger than 5 years.