Introduction: Breast milk is the most suitable feeding for all newborns and has numerous benefits widely described in the literature. For the extraction of milk, the suckling function of the newborn depends on adequate functioning of the tongue, including the lingual frenum. However, it is unclear the relationship among the lingual frenum and breast feeding. Purpose: To evaluate the lingual frenum in newborn infants and to verify their association with breast feeding. Methods: The sample consisted of 139 mother/infant binomials, who were born full term. For the anatomy-functional evaluation of the lingual frenum, the "Evaluation protocol of the lingual frenum for infants" was used. For the evaluation of the breast feeding, the "UNICEF observation protocol of breast feeding" was applied. To verify the association among the lingual frenum and breast feeding, the chi-square test was applied. Results: In the evaluation of the lingual frenulum of the 139 infants, it was verified only one infant with a frenum alteration, equivalent to a prevalence of 0.8%, was found. In the evaluation of breastfeeding, of the 138 binomials, whose infants did not have alteration of the lingual frenum, 82 of them (59.4%) did not demonstrated any difficulty during breast feeding. The only infant with lingual frenum alteration did not present difficulties in breast feeding. Conclusion: There are insufficient subsidies to establish an association among lingual frenum and breast feeding.