Objective: To determine the prevalence of malocclusion and associated factors in children and the level of knowledge of mothers participating in the child care group of a basic health unit. Material and Methods: This is a cross-sectional study conducted in children between 18 and 72 months of a childcare group in Pelotas. Children whose parents or legal guardians signed the informed consent term participated in the study. Data were collected through a questionnaire previously tested and applied to the mothers, and a clinical examination of children's occlusion were performed by examiners after training and calibration. Statistical analysis was descriptive and analytic. In the bivariate analyses, it was used the Pearson, Fisher or Linear Trend Qui-Square tests and, in the multivariate analysis, the Poisson regression. Prevalence ratios and 95% confidence intervals were obtained, and a p-value <0.05 was used. Results: Forty-seven children were included and 41.3% presented malocclusion. The prevalence of malocclusion was associated with a higher number of children in the family (p<0.005) and breastfeeding for more than 12 months (p<0.05). The highest prevalence of open bite was associated with the use of a pacifier and working mothers (p<0.05). Conclusion:Most mothers reported having knowledge about the time and use of pacifiers in childhood. In this group, the prevalence of malocclusion in children was high and associated with behavioral and social factors.