Acquired hemophilia A (AHA) is a rare autoimmune disease caused by autoantibodies against coagulation factor VIII and characterized by spontaneous hemorrhage in patients with no previous family or personal history of bleeding. We report here a case of AHA that occurred in the Department of Medicina D'Urgenza in Sant'Andrea Hospital in a patient with previous diagnosis of NSLC. The aim of this article is to allow a more comprehensive knowledge of AHA that both for the rarity and the poor literature is underdiagnosed; for all these reasons, it is important that different specialists, like emergency specialists, experts in internal medicine, hematologists, and oncologists, acquire a more complete knowledge of the clinical and laboratory features of this disease, allowing an early diagnosis crucial for the evolution of the coagulopathy.