Abstract Background: Neonatal hyperbilirubinemia (NH) is among the common neonatal morbidities. Phototherapy is its most used therapeutic intervention. Different delivering systems and types are currently available. Aim of Study: The aim of the study was to evaluate the electrolyte changes in neonates receiving phototherapy with find out the high risk neonates for electrolyte changes and to compare the effect on electrolytes in preterm and term neonates receiving phototherapy. Subjects and Methods: This was a clinical trial, the study was conducted in special care baby unit at Al-Wahda Teaching Hospital, Derna, Libya over a period of six months from August 1st 2021 to February 2022. Sixty newborns 34 Male, 26 Female were enrolled in the study. Results: There was a significant decrease in total bilirubin, sodium, calcium, and magnesium levels after phototherapy. However, there is a slight change in potassium, chloride, phosphorous, and ALP but without statistically significant difference. Conclusion: Serum electrolytes significantly decreased during phototherapy. This study shows that neonates exposed to phototherapy are at a risk of developing electrolyte imbal-ances and consequently their complications. Hence, close monitoring of such babies are needed to prevent imbalances and their untoward consequences.