Background <p>Severe hemolytic disorders in neonates can lead to anemia, jaundice, and potentially severe neurological impairment or death. Early intravenous immunoglobulin (IVIG) administration has gained attention for its potential to mitigate hemolysis and its complications. But the optimal timing of IVIG remains a topic of debate. Therefore, this study aims to investigate the influence of early IVIG administration on the prognosis of severe hemolytic disorders in neonates.</p> Methods <p>A retrospective analysis of clinical data from 58 cases of neonatal severe hemolytic disease admitted to hospital (January 1, 2022-December 3, 2025) was conducted. The cases were divided into an early IVIG (<i>n</i> = 29) and control (<i>n</i> = 29) groups based on whether immunoglobulin was administered within 12&#xa0;h of birth. Baseline characteristics, hemoglobin values, total bilirubin levels, cumulative phototherapy time, and incidence of complications were assessed.</p> Results <p>Baseline characteristics were well-matched between the two groups. Hemoglobin levels at 7 days after treatment in the early IVIG group was significantly decreased compared to control. The cumulative phototherapy duration in the early IVIG group was also significantly higher than control. Furthermore, the early IVIG group had a significantly higher incidence of severe jaundice. Correlation analysis showed significant associations between early IVIG administration and hemoglobin levels, cumulative phototherapy time, and the incidence of severe jaundice.</p> Conclusion <p>Early IVIG administration in neonates with severe hemolytic disorders may be associated with a more rapid decline in hemoglobin levels, prolonged duration of phototherapy, and increased incidence of severe jaundice.</p> Trial registration <p>Not applicable.</p>