One of the most challenging decisions is to assess the preterm infant's transition from tube feeding to oral feeding. Thus, we require a reliable tool for determining the time to start oral feeding. This study aimed to measure the interrater and intrarater reliability of the Preterm Infant Oral Feeding Readiness Assessment scale (PIOFRA). Materials and Methods:This study was an observational, cross-sectional study. The study participants were preterm infants who had been hospitalized in the Neonatal Intensive Care Unit of Shariati Hospital affiliated to Tehran University of Medical Sciences, between December 2017 and February 2018. The inclusion criteria were absence of neurological and gastrointestinal disorders or major congenital anomalies, Apgar score 3 or more in the first 1 minute, and 5 or more in the first 5 minutes. The exclusion criteria included family's unwillingness to participate in the study, infant's death, or a sudden change that affects neonates' nutritional status, like cerebral hemorrhage or intestinal problems. Results:The interrater and intrarater reliability of the total PIOFRA scale was good Intraclass Correlation Coefficients (ICC˃0.75). The interrater and intrarater reliability of most items were good and excellent, with weighted kappa more than 0.50, with the exception of lip posture and especially stress sign, with weighted kappa less than 0.40. Conclusion:Generally, most items of the PIOFRA scale had acceptable interrater and intrarater reliability. Also, the interrater and intrarater reliabilities of the total POFRAs score was good.