Background: Childhood immunization saves the lives of 2-3 million children annually by protecting them against vaccine-preventable diseases. In 2017, 116.2 million children were vaccinated worldwide according to the World Health Organization. Nevertheless, figures suggest that 19.5 million children around the world fail to receive the benefits of complete immunization. Methods: This cross-sectional study analyzed vaccine uptake and the factors associated with compliance in all the children of up to 36 months of age receiving care within the family health strategy program in an irregular settlement located in a state capital city in northeastern Brazil. This study was nested within a larger study entitled “Health, nutrition and healthcare services in an urban slum population in Recife, Pernambuco”, conducted in 2015. A census sample of 309 children was included, with vaccination data being obtained from their personal child health records. An ad hoc database was constructed, with absolute and relative values being calculated for the socioeconomic, demographic, obstetric and biological data collected. To identify possible factors associated with vaccine compliance, univariate and multivariate regression analyses were performed, and the 95% confidence intervals calculated. Variables with p-values <0.20 in the univariate stage were included in the multivariate analysis. The statistical significance of the variables was evaluated using the Wald test, with p-values <0.05 being considered statistically significant. Results: Compliance with the vaccination schedule was 52.1%. In the final model, the factors associated with inadequate compliance with the vaccination schedule were age 12-36 months and the mother not having completed high school. Conclusion: The percentage of vaccine uptake found was well below the figure recommended by the national immunization program and was associated with the child’s age and the mother’s education level. Based on these findings, the family healthcare teams may elaborate vaccination strategies aimed at reaching the coverage rates established by the national immunization program. Optimizing coverage will ultimately prevent the resurgence, at epidemic level, of infectious diseases that are already under control in this country. Keywords: children’s health; vaccination schedule; maternal education level; Family Health Strategy.