Introduction: Neonatal hyperbilirubinemia is a common problem. Approximately 60% of term infants and 80% of preterm infants develop jaundice in the first week of life. Despite hyperbilirubinemia being a common morbidity among neonates, few studies have systematically studied the phenomenon of post‐phototherapy rebound, data about the phenomenon of bilirubin rebound is lacking.Objectives: The aim of this study was to determine whether a rebound in serum bilirubin level occurs within 24 hours after discontinuation of phototherapy in neonates with hyperbilirubinemia and to identify aetiological factors for hyperbilirubinemia that could be used to select infants at risk for rebound.Study design: A prospective clinical survey was performed on 133 term and preterm neonates treated with phototherapy. Neonates were tested for T.S.B 24(±6) hours after discontinuation of phototherapy, with additional testing as clinically indicated. The main outcome measure, significant bilirubin rebound, was defined as a post-phototherapy T.S.B ≥15 mg/dl. Phototherapy was not reinstituted in all cases of rebound, but rather according to clinical indications.Results: A total of 29 (21.8%) neonates developed significant rebound, mean (±SD) T.S.B was 16.45 (±0.99) mg/dl. Multiple logistic regression analysis for risk factors for significant bilirubin rebound showed significant risk for aetiological risk factors including hemolysis (odds ratio 1.241, 95% CI 1.117 to 2.496) and positive direct Coombs test (odds ratio 6.392, 95% CI 1.530 to 26.706). Sixteen of those (55.2%) were retreated with phototherapy, mean (±SD) T.S.B was 16.9 (±1.1) mg/dl. Multiple Logistic regression analysis for risk factors for re-admission for phototherapy showed significant risk for aetiological risk factors including hemolysis (odds ratio 1.121, 95% CI 1.048 to 2.307) and positive direct Coombs test (odds ratio 7.162, 95% CI 1.571 to 32.658). Also there was a trend for re-admission for phototherapy with weight < 2kg (odds ratio 5.976, 95% CI 0.818 to 43.685).Conclusion: Post-phototherapy neonatal bilirubin rebound to clinically significant levels may occur, especially in cases of hemolysis, direct Coombs test positivity and low birth weight < 2kg. These risk factors should be taken into account when planning post-phototherapy follow up.