The aim of this study was to investigate the relationship between feeding practices in the first year of life and the occurrence of severe early childhood caries (S-ECC) at 4 years of age. A birth cohort study (n = 500) was conducted in children who were born within the public health system in São Leopoldo, Brazil. Feeding practices were assessed using standardized methods at 6 and 12 months of age. A total of 340 children were examined at 4 years of age. S-ECC was defined as recommended by an expert panel for research purposes: ≧1 cavitated, missing or filled smooth surfaces in primary maxillary anterior teeth or d1+ mfs ≧5. Poisson regression with robust variance was used in order to determine the early feeding practices which represent risk factors for the occurrence of S-ECC at 4 years of age. The multivariable model showed a higher adjusted risk of S-ECC for the following dietary practices at 12 months: breastfeeding ≧7 times daily (RR = 1.97; 95% CI = 1.45–2.68), high density of sugar (RR = 1.43; 95% CI = 1.08–1.89), bottle use for liquids other than milk (RR = 1.41; 95% CI = 1.08–1.86), as well as number of meals and snacks >8 (RR = 1.42; 95% CI = 1.02–1.97). Mother’s education ≤8 years was also associated with the outcome. The present study identified early feeding practices which represent risk factors for caries severity in subsequent years. These findings may contribute to developing general and oral health interventions, with special attention to families with low maternal education.