Aims: Acquired haemophilia A is a rare but critical differential in patients presenting with atraumatic sublingual swelling and impending airway compromise, which may mimic deep neck space infection. Methodology: A 74-year-old male presented with a 24-hour history of progressive floor-of-mouth swelling, dysphonia, and respiratory distress. Clinical examination, flexible laryngoscopy, cross-sectional imaging, and laboratory investigations were reviewed. A haematological diagnosis was made in collaboration with haematology to guide management. Results: On presentation, the patient demonstrated features of a threatened airway, including inability to lie supine, stertor, and progressive respiratory distress. Examination revealed marked sublingual and submental swelling with tongue elevation, mimicking Ludwig’s angina. Flexible transnasal laryngoscopy showed supraglottic haemorrhagic oedema. Although Ludwig’s angina was initially suspected, inflammatory markers were not consistent with infection. CT imaging demonstrated sublingual and submental fat stranding without a drainable collection. Laboratory investigations revealed an isolated prolonged activated partial thromboplastin time (APTT) of 64 seconds, which corrected on mixing studies, suggesting an acquired coagulation disorder. The patient also exhibited systemic features of coagulopathy, including petechiae, epistaxis, and gingival bleeding. He was admitted to the intensive care unit for close airway monitoring, with preparedness for awake fibreoptic intubation. Haemostatic therapy included tranexamic acid, fresh frozen plasma, recombinant activated factor VII, prothrombin complex concentrate, and corticosteroids. Rapid clinical improvement occurred without airway intervention. Conclusion: Coagulopathy should be considered in atraumatic sublingual haematoma with atypical infective features. Early recognition is essential to guide appropriate management and avoid unnecessary surgical intervention.