Simultaneous onset of autoimmune hemolytic anemia (AIHA) and pure red cell aplasia (PRCA) is rare and any possible association between these two disorders remains obscure. A 46-year-old previously healthy woman was diagnosed as having AIHA based on severe anemia, positive direct and indirect Coomb's tests, decreased serum haptoglobin, elevated serum LDH, and indirect bilirubin-dominant hyperbilirubinemia. Oral steroid administration (1 mg/kg) and subsequent half-pulse steroid therapy ameliorated the AIHA, but the anemia was unexpectedly prolonged with the low peripheral blood reticulocyte count further decreasing to 0.11%. Bone marrow aspiration revealed a marked decrease in erythroblasts with an M/E ratio of 69.5. Anti-parvovirus B19 IgM antibody and serum B19 viral DNA (109 copy/ml) were detected but no other distinct abnormalities which might have caused acquired PRCA were detected. Therefore, she was considered likely to have idiopathic AIHA and acquired PRCA simultaneously. AIHA-mediated erythroblastosis probably raised the parvovirus B19 DNA level to an extraordinary degree and thereby led to severe aplastic crisis, subsequently causing prolonged anemia. Parvovirus B19 infection should be considered in AIHA patients showing unexpectedly low reticulocyte counts.