A 25-year-old previously healthy pregnant woman was admitted to our hospital because of severe anemia (Hb 6.7 g/dl), and diagnosed as having mixed-type autoimmune hemolytic anemia (AIHA) due to de novo cytomegalovirus (CMV) infection. After daily administration of prednisolone, the anemia gradually resolved and the patient delivered a healthy baby. This is the first report of a healthy person suffering from mixed-type AIHA due to de novo CMV infection.