Acquired hemophilia A (AHA) is a rare bleeding disorder, caused by autoantibodies inhibiting the function of coagulation factor VIII. The disease is characterized by either spontaneous or induced hemorrhage in patients with no previous family or personal history of bleeding. In contrast to congenital hemophilia A, this disorder tends to occur later in life in male or female patients without previous coagulation disorder, and the bleeding phenotype is quite different. In most cases, bleeding leads to further diagnostic workup and the recognition of AHA. The properties of AHA are well known since many years from large registries, case series, and some prospective studies, and international management guidelines have been established. This chapter summarizes the current knowledge on the characteristics of AHA and the necessary diagnostic approach and gives an overview on the latest data on optimal and individual therapeutic management.