Objective: Late preterm infants are known to be at a higher risk of morbidity and mortality, although they were previously thought to be as physiologically and metabolically mature as term infants. In twin, late preterm infants represent the majority of premature infants, but little is known about their pregnancy outcomes. The aim of this study was to evaluate the short and long term outcomes of late preterm in twin pregnancy. Methods: This study was conducted by merging the databases of the Korea National Health Insurance claims, and a National Health-Screening Program for Infants and Children. We identified all women who had twin delivery between January 1, 2007 and December 31, 2010. The primary short-term outcome was composite morbidity which includes any of the following: transient tachypnea, respiratory distress syndrome, necrotizing enterocolitis, intraventicular hemorrhage, and bronchopulmonary dysplasia. For long-term outcomes, all neonates were followed-up until end of 2018, by the time they were 811 years of age. Long term outcome was defined by prespecified neurologic and developmental diagnoses using ICD-10 code. Results: Compared with twin offspring born in term, twin offspring born in late preterm had adverse short term outcomes including transient tachypnea (OR 1.92, 95% CI 1.70, 2.16), RDS (OR 2.19, 95% CI 1.94, 2.47), necrotizing enterocolitis (OR 1.84, 95% CI 1.07, 3.19) and intraventicular hemorrhage (OR 2,40, 95% CI 1.66, 3.47) on multivariate analysis. For long-term outcomes, twin offspring born in late preterm had also increased risk for any neurological or neurodevelopmental delay (HR 1.12, 95% CI 1.04, 1.20). Conclusion: Our study shows that twin offspring born in late preterm are at a high risk of short and long term morbidity.