Not much is known about how health insurance affects preventive care for children who have access to general routine paediatric care, especially in less developed settings. This study evaluates the effects of child health insurance on preventive care (measured by whether the child had received all the age-appropriate immunizations) for children with access to routine paediatric care. It uses a unique sample of 1958 children aged 3–24 months attending paediatric practices for routine well-child care in Argentina, Brazil and Ecuador.