Fetomaternal hemorrhage is referred to as the passage of fetal blood into the maternal circulation. Massive hemorrhage can cause severe fetal anemia, affecting fetal and neonatal outcomes. A neonatal hemoglobin concentration (Hb), which is reportedly a significant prognostic factor, of <5.0 g/dL has been reported to carry a high risk of poor outcomes (death and major morbidity). We present a case of massive fetomaternal hemorrhage with the lowest value of neonatal Hb ever previously reported in a survivor, who subsequently met all the developmental milestones at the corrected age of 18 months. A male infant born at 27 weeks gestation, weighing 998 g, presented with severe anemia with an Hb of 1.2 g/dL and an HbF level in the mother's blood of 2.4%, which led to a diagnosis of fetomaternal hemorrhage. Since there were no findings of hypovolemia, exchange transfusion was performed for prompt correction of the severe anemia without precipitating volume overload. The present case suggested that exchange transfusion might promptly correct anemia in patients with fetomaternal hemorrhage without hypovolemia without causing volume overload.