ObjectiveTo describe the epidemiology and risk factors for hospitalisation and death in Mexican children under 18 years of age with COVID-19.DesignRetrospective, cross-sectional and analytical study.SettingMexican Ministry of Health open databases with COVID-19 cases occurred from 7 March 2020 to 30 September 2021.ParticipantsMexican children under 18 years of age with COVID-19.Main outcome measuresCOVID-19 hospitalisations and deaths were characterised by age group, sex, presence of pneumonia and comorbidities, intubation and intensive care unit admission, and institution that provided medical care. Cumulative incidence, mortality, case fatality rates and ORs for hospitalisation and death were estimated by age group.Results5.5% (204 641) of national COVID-19 cases were children under 18 years of age: 2.9% under 1 year, 12.5% from 1 to 5 years, 15% from 6 to 9 years and 69.4% from 10 to 17 years. 4.6% of all cases were hospitalised, from which 54.6% were male, 35.3% were children under 1 year old, 39.6% were adolescents and 34% had pneumonia. Pneumonia developed in 2.3% of cases, from which 50% were adolescents. Case fatality rate was higher in children less than 1 year old (4.2%). Risk analyses showed that male sex (OR 1.16–1.28), history of pneumonia (OR 29.7–65.4), immunosuppression (OR 5.3–42.9), cardiovascular disease (OR 4.4–14.6) and other comorbidities (OR 5.4–19.1), as well as age less than 1 year (OR 20.1, 95% CI 18.8 to 21.4), confer a greater risk of hospitalisation; in addition to comorbidities, age less than 1 year (OR 16.6, 95% CI 14.1 to 19.6), history of pneumonia (OR 14.1–135.1) and being an adolescent from an indigenous community (OR 2.6, 95% CI 1.23 to 5.54, p=0.012) increase the risk of death.ConclusionsIn Mexico, children less than 1 year old with COVID-19 have higher risk of hospitalisation and death than older children. Adolescents with COVID-19 in association with comorbidities develop adverse outcomes more frequently.