Background: Zinc salts can reduce phototherapy duration by precipitating unconjugated bilirubin in the intestine however, zinc toxicity is an issue that must be considered. Theoretically, bilirubin reduction by phototherapy may increase serum zinc levels, making additional zinc supplementation, which cause zinc toxicity. Objectives: To evaluate serum zinc level alterations before and after phototherapy in hyperbilirubinemic newborns. Materials and Methods: A prospective cross sectional case-control study was performed at Neonatal Intensive Care Unit (NICU),