Infants with posterior tongue-tie (PTT) can have substantial difficulty with breastfeeding and bottle-feeding. This study aimed to address the dearth in investigational objective data surrounding PTT release to better quantify the postoperative impacts of frenotomy for ankyloglossia. Prospective randomized, controlled trial. Private practice clinic. In a prospective, randomized controlled trial, infants 3 to 16 weeks of age with PTT undergoing frenotomy were examined using a bottle-feeding system capable of objectively measuring tongue function. Validated patient-reported outcome measures were also obtained simultaneously. Forty-seven infants with PTT were enrolled into an observational/control arm (n = 23) or interventional/surgical treatment arm (n = 24). The total cohort consisted of 29 (61.7%) male infants with a median age of 39 days. At the day 10 time point, the interventional arm demonstrated statistically significant improvement in 11 objectively obtained feeding metrics, indicating faster tongue speed, more rhythmic and coordinated sucking motions, and a tongue more capable of adapting to varying feeding demands. Significant improvement in breastfeeding self-efficacy was reported in the interventional group while poor self-confidence persisted in the observational group. Infant reflux symptoms improved in the interventional group while not in the control group. Nipple pain also persisted in the control group but improved in the surgical cohort. When measured 10 days after frenotomy for PTT, infants improve feeding parameters using an objective bottle-feeding system. Similar improvements are seen with patient-reported outcomes when PTT is released. Posterior tongue-tie is a valid clinical concern, and surgical release can improve infant and maternal symptoms.