Hyperbilirubinemia is the most common abnormal physical finding in first few weeks of lif and its most common management is phototherapy. Amongst other common complications a less known complication of phototherapy is hypocalcemia. Objectives: To study the incidence of phototherapy induced hypocalcemia in neonates and to have a comparison between preterm and term neonates. Study design: Descriptive cross-sectional study. Setting: Paediatric Unit II DHQ Hospital Faisalabad, which is a tertiary care centre for all kind of patients. Duration of study with dates: Six months from 1-11-2012 to 30-04-2013. Methods: 196 neonates with hyperbilirubinemia full term / preterm neonates admitted in pediatric DHQ hospital faislabad were selected. Inclusion criteria. 1) Hyperbilirubinemia. 2) No hypocalcemia on admission. 3) Received phototherapy for hyperbilirubinemia. Serum Calcium levels were measured in all neonates before and 48 hours after receiving phototherapy. Incidence of hypocalcemia among all neonates was calculated as an absolute percentage and the sample population was also divided into preterm / full term neonates to evaluate the incidence of hypocalcemia in these two groups individually. RESULTS: Mean serum calcium in neonates was 7.5+-1.5 mg / dl .16.84 % of neonates were found to have calcium level below the cut off value. 33 out of 196 developed hypocalcemia after phototherapy and out of these 54 % were preterm and 45 % were term neonates < P-value (0.01)>. Conclusion: Phototherapy induces hypocalcemia in neonates more so in preterm neonates. Impact: Consideration for additional calcium supplementation should be undertaken in all neonates undergoing phototherapy and further randomized trials need to be done with these concerns.