Aim The objective of the present research was to compare the nutritional status, weight gain, length of hospital stay, and the development of some complications in very low birth-weight (VLBW) infants who received and those who did not receive olive oil supplementation enterally. Materials and Methods This study was a single-blind, randomized controlled trial with 96 VLBW infants (intervention: 48, control: 48) in a neonatal intensive care unit. In this study, those infants who met the inclusion criteria for the study were divided into two groups by using a random number table. The same feeding protocol (breast milk and/or formula milk) was applied to the infants in both groups. From the seventh day of life (after starting to take 25-30 mL/kg/day orally), 0.5 cc/30 mL of olive oil was added to the milk at each feeding of those infants in the intervention group. RESULTS In comparison with the control group, the infants in the intervention group had a higher daily weight gain rate in the first month and a higher weight on the tenth day, a shorter transition time to full enteral feeding, a higher amount of calories on the day of transition to full enteral feeding, and a shorter length of hospital stay (p<0.05). Furthermore, the need for rectal enema and the prevalence of sepsis, gastrointestinal system intolerance, and bronchopulmonary dysplasia were significantly lower in the intervention group in comparison with the control group (p<0.05). CONCLUSION These findings suggest that olive oil supplementation administered enterally to preterm infants can be recommended since it positively affects the development of infants. Trial registration: This study was registered in ClinicalTrials.gov with the following ID: NCT05815849. This study was retrospectively registered on the 14th of April, 2023.