Background: As opposed to congenital cases, acquired Haemophilia A (AHA) is caused by the formation of autoantibodies against Factor VIII which increases a patient’s propensity to bleed. Approximately 50% of AHA cases have no identifiable trigger, and overall incidence is estimated at 1 per 1.5 million people. In the surgical patient, unrecognised bleeding disorders can be catastrophic. Case Report: We present a case of AHA in a 75-year-old male undergoing excision of a Merkel Cell Carcinoma with cheek rotation flap reconstruction at the Gold Coast University Hospital. Within 48 hours from his initial excision and reconstruction, the patient returned to the operating room for a significant post-operative haematoma. Whilst the patient had no personal or family history of bleeding diathesis, Haematology consultation led to the diagnosis of AHA with a Chromogenic Factor VIII level of <1%, an inhibitor titre of 870 BU and an APTT of 127 on post-operative coagulation studies. This case was considered idiopathic due to the challenges in identifying exact triggers in this condition. Treatment with NovoSeven peri-procedurally, corticosteroids, Rituximab and Emicuzimab led to some improvement in his condition. Literature Review: AHA is rare, and unexplained post-operative bleeding can prompt investigation and diagnosis. While response to first line therapies is fair, the delay in identifying the condition and the time taken for treatment to be effective can cause morbidity and mortality in surgical patients. Conclusion: We present this case as a potential differential diagnosis in surgical patients with persistent or otherwise unexplained post-operative bleeding and review existing literature on similar cases.