Aim To investigate risk factors for the occurrence of traumatic dental injuries (TDI) at 4years of age. Design Prospective cohort study. Methods A birth cohort (n=500) was recruited from the public healthcare system in Sao Leopoldo, Brazil. Demographic, socioeconomic, anthropometric, and behavioral variables were collected at 6months, 1year, and 4years of age. Clinical examinations at 4years of age were carried out by a single examiner using the Andreasen classification. Poisson regression was used to determine risk factors for the occurrence of TDI at 4years of age. Results A total of 23.7% of the children (80/337) exhibited TDI at 4years of age. The risk of TDI was 35% lower among children who had been breastfeed for >= 6months relative risk (RR 0.65; 95% CI 0.43-0.97) and more than twofold higher among those who were bottle fed >= three times a day (RR 2.37; 95% CI 1.10-5.11) at 12months of age. Higher household income in the first year of life and greater height at 4years of age were significantly associated with the outcome. Conclusions The identification of behavioral, socioeconomic, and anthropometric risk factors for TDI in early childhood can contribute to the elaboration of prevention strategies.