Introduction: Nephrocalcinosis is a relatively common clinical condition in preterm infants, and the prevalence of nephrocalcinosis in premature infants ranges from 7% to 41 % in the different studies. Nephrocalcinosis in preterm neonates are known to be affected by multifactorial etiologies such as low gestational age, low birth weight, bronchopulmonary dysplasia, fluid restriction and other various causes. The aim of this study was to evaluate the prevalence and the risk factors of nephrocalcinosis in Korean infants born preterm. Method: We retrospectively analyzed the medical records of 27 preterm infants who were admitted to a neonatal intensive care unit from January 2015 to December 2016 and diagnosed as having nephrocalcinosis during hospitalization and 1-year follow-up. The diagnosis of nephrocalcinosis was made by the medical history and renal ultrasonography. Result: The prevalence of nephrocalcinosis in Korean infants born preterm is 4.1%. The median age at the time of diagnosis was 72 days (17 - 548 days), and the male-to-female ratio was 1.1:1. The median gestational age was 28.8 weeks and body weight at birth was 1149.4±693.5 grams. The risk factors of nephrocalcinosis included patent ductus arteriosus (n=13, 48.1 %), bronchopulmonary dysplasia (n=11, 40.7%), the use of vitamin D (n=23, 85.2%), and diuretics (n=5, 18.5%). The serum levels of calcium and phosphorous at the time of diagnosis were 10.3±1.0 and 5.7±1.1 mg/dL, respectively. The hospitalization period was 119.3±63.4 day, and 2 patient died during follow-up. Although nephrocalcinosis persisted in 8 patients during the first year of life, only 3 patients visited the outpatient clinic of pediatric nephrology. Conclusion: The prevalence of nephrocalcinosis in Korean infants born preterm was relatively low. Nephrocalcinosis in preterm infants might be associated with impaired renal function in the future, and the cooperation between the neonatologists and nephrologists is necessary. Future research for interventions to prevent nephrocalcinosis in preterm infants is crucial.