The congenital dyserythropoietic anemias (CDAs) are a heterogeneous group of genetic disorders of red cell production. They are characterized by ineffective erythropoiesis and dyserythropoiesis. Here, we present the clinical description and mutation analysis of a Japanese female with CDA type 1. She has long been diagnosed with unclassified congenital hemolytic anemia from the neonatal period. However, bone marrow morphology and genetic testing of the CDAN1 gene at the age of 12 years confirmed the afore-mentioned diagnosis. Thus, we should be aware of the possibility of CDA if the etiology of congenital anemia or jaundice cannot be clearly elucidated.