Three cases of severe neonatal anemia due to fetomaternal transfusion are reported. The key features that lead to early diagnosis were the maternal history, fetal monitoring, the clinical and laboratory findings of anemia, and a negative Coombs test. Diagnosis was confirmed by a rapid Kleihauer-Betke test. A partial exchange transfusion was performed in two of the three neonates with rapid clinical and hematological improvement. As two patients showed signs of heart decompensation, a partial exchange transfusion was performed with good success. In patients presenting with severe subacute or chronic anemia and heart failure, a partial exchange transfusion may be preferable to that of simple transfusion associated with diuretics.