Abstract Background: Hyperbilirubinemia is a prevalent neonatal issue, with jaundice occurring in 60% of term neonates and 80% of preterm neonates during the first week of life. Aim of Study: To assess the effect of phototherapy on serum calcium level in full term neonates with indirect hyperbiliru-binemia. Patients and Methods: This prospective interventional study was conducted on 50 full term neonates with indirect hy-perbilirubinemia at the neonatal intensive care unit (NICU) of National Liver Institute, Menoufia University and (NICU) of Al-Mahala Alkobra General Hospital starting from February 2018 till March 2020. Results: Mean TSB (pre) was 16.87 and ranged from 8.1 to 21, mean TSB (post) was 9.54 and ranged from 5 to 14.3, mean ionized Ca (pre) was 4.92 and ranged from 4.24 to 5.8, mean ionzed Ca (post) was 4.94 and ranged from 4.1 to 6.5, mean Phosphorus (pre) was 6.39 and ranged from 4.7 to 8.4, mean Phosphorus (post) was 7.23 and ranged from 4.5 to 8.9 and mean PTH (pre) was 40.18 and ranged from 15 to 103, mean PTH (post) was 61.52 and ranged from 14.44 to 107. There was no significant difference between ionized Ca pre and post phototherapy in neonates who received single or dou-ble phototherapy p>0.05, Significant increase in PTH pre and post phototherapy inneonates who received single and double phototherapy p<0.05, no significant difference between phos-phorus pre and post phototherapy in neonates who received single phototherapy p=0.155 and significant increase in phos-phorous post phototherapy in neonates who received double phototherapy p=0.001. Conclusion: Regarding Phototherapy Effects on Neonates, we concluded that there was no significant difference in ionized Ca pre and post Phototherapy and Significant increase in PTH pre and post Phototherapy.