Background: Preterm infants are at risk of iron deficiency (ID). Hepcidin has been suggested as a good additional indicator of ID in preterm infants, next to ferritin. Methods: In a prospective observational study, we analyzed serum hepcidin in 111 infants born after 32+0 to 36+6 wk gestational age during the first 4 mo of life. Results: Hepcidin concentrations decreased during the first 4 mo of life, and concentrations were lower in infants with ID compared to those without ID. Infants who developed ID at the age of 4 mo had already significantly lower levels of hepcidin at 1.5 mo of age, while ferritin was already significantly lower at the age of 1 wk. Conclusion: Hepcidin concentrations of late preterm infants decrease during the first 4 mo of life. This decrease, which parallels a decrease of ferritin concentration, we interpret as a physiological response, aiming to increase iron availability. Hepcidin concentrations are lower in infants with ID compared with those without ID, with a notable change already observed at 1.5 mo of age. Hepcidin can be used as an early marker of ID, although an additive value of hepcidin over ferritin in the diagnosis of ID is not present.