Phototherapy is the standard treatment in moderately severe hemolytic disease of newborn (HDN), whereas exchange transfusion (ET) is the second line in progressive cases. Intravenous immunoglobin (IVIG) has been suggested to decrease the need for ET. We aimed at assessing the efficacy of early two-dose regimens of IVIG to avoid unnecessary ET in severe Rh HDN. The study included 90 full-term neonates with Rh incompatibility unmodified by antenatal treatment and not eligible for early ET and which were randomly assigned into one of three groups: group (I), treated by conventional method; groups IIa and IIb received IVIG once at 12 h postnatal age if PT was indicated, in a dose of 0.5 and 1 g/kg, respectively. Analysis revealed 11 neonates (22%) in the conventional group and 2 (5%) in the intervention group who administered low-dose IVIG at 12 h, while none in group IIb required exchange transfusion (p = 0.03). Mean bilirubin levels were significantly lower during the first 96 h in the intervention group compared to the conventional group (p < 0.0001). Shorter duration of phototherapy (52.8 ± 12.39 h) and hospital stay (3.25 ± 0.71 days) in the IVIG group compared to conventional group (84 ± 12.12 h and 4.72 ± 0.78 days, p < 0.0001, respectively) were observed. We conclude that IVIG administration at 12 h was effective in the treatment of severe Rh HDN; the low-dose IVIG (0.5 g/kg) was as effective as high dose (1 g/kg) in reducing the duration of phototherapy and hospital stay, but less effective in avoiding exchange transfusion.