Introduction: The Bombay blood phenotype (Oh) is an exceptionally rare variant where individuals lack the H antigen and produce anti-H, anti-A, and anti-B antibodies. When mothers with this phenotype deliver infants with conventional blood types, maternal antibodies can cross the placenta, potentially triggering severe hemolytic disease. Case presentation: A 29-year-old woman with Bombay O phenotype delivered a 2.785 kg maleinfant at 35+6 weeks gestation as her third child. The pregnancy was uncomplicated. Within 24 hours of birth, the neonate developed rapidly progressive jaundice with indirect hyperbilirubinemia exceeding exchange transfusion thresholds, without hepatosplenomegaly .Laboratory evaluation revealed blood type O Rh D positive with negative direct antiglobulin test. Hematologic studies showed hemoglobin 11.6 g/dL, reticulocytosis (15%), and spherocytosis on peripheral smear. Although total bilirubin reached exchange transfusion levels on day one, Bombay O blood was initially unavailable. The infant received triple phototherapy and IVimmunoglobulin. Subsequently , Bombay O blood transfusion corrected the anemia. Bilirubin levels stabilized and gradually declined, permitting discharge on day seven. Conclusion: This case illustrates the complex management of neonatal hyperbilirubinemiaassociated with the rare Bombay phenotype, where multiple maternal antibodies create severe hemolysis beyond typical ABO incompatibility . Clinicians should consider atypical blood group incompatibilities when jaundice progresses rapidly within 24 hours of life. Early recognition, intensive phototherapy , IV immunoglobulin, and timely exchange transfusion are crucial for preventing kernicterus. Prenatal identification of rare blood phenotypes should trigger appropriate planning to optimize neonatal outcomes.