Background: The present study aims to test the effect of the Safe Individualized Nipple-Feeding Competence (SINC) protocol on the preterm infants’ weight gain, transition to oral feeding, and duration of hospitalization. Methods: The procedure was designed as a single-blind, parallel-group randomized controlled trial. The trial was conducted in a neonatal intensive care unit (NICU) in Konya, Turkey. Data were collected from 80 preterm infants between February 2018 and March 2019. Infants (gestational weeks 28–33) were randomly assigned to the intervention (n = 39) and control groups (n = 41). The intervention group received the SINC feeding protocol, whereas the control group received the standard feeding. Data were collected using the Family Information Form, the Preterm Infant Follow-Up Form, and the SINC Protocol Evaluation Checklist. Infants were followed from hospitalization to discharge. The outcomes were weight gain, transition to oral feeding, and the length of hospitalization from birth to discharge. Pearson χ2 test, Fisher exact test, independent t-test, Mann-Whitney U test, and general linear model test were used in analyzing the data. Results: The main effects of groups on weight measurements were found to be statistically significant (P <.001). There were no significant differences in terms of the transition from gavage to full oral feeding and the length of hospitalization (P >.05). Conclusions: SINC protocol positively influences weight gain in preterm infants. It is important to evaluate different evidence-based feeding methods both as they apply to the NICU stay and how they may affect long-term outcomes of preterm infant.