Congenital hemophilia A, a relatively common and sometimes life-threatening bleeding disorder, is caused by inherited deficiency of clotting factor (F) VIII. The adoption of an appropriate medical and environmental prophylaxis is critical for long-term management of hemophilia because it will considerably reduce the number of both mild and severe bleeding episodes. Among the many therapeutic options that have become available over the past decades, ACE910 (also known as emicizumab) is a bispecific immunoglobulin G antibody characterized by its unique ability to bind FIX or FIXa on one arm and FX on the other, thus abrogating FVIII activity in vivo. Several phase I to III clinical trials have now been published, confirming the clinical efficacy and relative safety of this new agent for long-term prophylaxis of hemophilia A, especially those patients having FVIII inhibitors. The recent regulatory clearance of ACE910 in many countries will hence impose additional challenges to clinical laboratories because the panel of available tests will need to address the emerging issue of monitoring patients treated with this novel anti-hemophilic agent by using conventional as well as innovative approaches. Therefore, this article is aimed to provide an update on clinical background and challenges of laboratory assessment in hemophilia A patients undergoing ACE910 administration.