Introduction The tongue plays an important role in the development of craniofacial structures. At rest, the light and constant pressure of the tongue against the hard palate, counterbalanced by the pressure provided by proper lip sealing, serves as a guide for maxillary growth. Ankyloglossia makes tongue coupling against the hard palate difficult, impacting maxillary development, which may lead to breathing disorders. Objective To verify the effect of lingual frenotomy on the resting position of the tongue and lips in infants with ankyloglossia. Methods The sample consisted of 334 infants aged between 1 and 60 days old diagnosed with ankyloglossia. The groups were divided in: a) experimental group (EG), which consisted of infants whose mothers agreed with lingual frenotomy; b) control group (CG), which consisted of infants whose mothers either refused lingual frenotomy or were waiting for surgery. Both the position of the lips and of the tongue at rest were assessed while the infants were sleeping during the quiet sleep phase. For mothers who refused their infants to undergo the surgical procedure, a follow-up of the infants was proposed to verify possible interference of the frenulum with the resting position of the tongue and lips. Infants whose mothers agreed with surgery were referred for lingual frenotomy. Results Regarding the position of the tongue and lips at rest at the initial and final assessments, the statistical analysis demonstrated significant differences between both groups. Conclusion Lingual frenotomy enabled infants diagnosed with ankyloglossia to maintain both tongue coupling against the hard palate and closed lips at rest.