Objectives. We present an exceptionally rare case of acquired hemophilia B coexisting with lupus anticoagulant (LA), with the concurrent presentation of bleeding and thrombosis. This unique and challenging case poses significant diagnostic and management difficulties for clinicians. Case presentation. A 45-year-old male presented with severe cephalgia, gastrointestinal bleeding, and a subacute subdural hematoma. Laboratory investigations revealed prolonged prothrombin time (PT) and activated partial thromboplastin time (aPTT), positive LA, and a significant reduction in factor IX levels. Despite receiving fresh frozen plasma (FFP) and packed red cells (PRC), the patient’s coagulation abnormalities persisted. Outcome. Further investigation led to the diagnosis of acquired hemophilia B with positive lupus anticoagulant. We suspected that a factor inhibitor or vitamin K deficiency might be contributing to the bleeding disorder, necessitating additional confirmatory diagnostics. The patient ultimately chose to be discharged against medical advice, highlighting the ongoing challenges in diagnosing and managing such complex conditions. Conclusions. Bleeding disorders in the presence of autoantibodies require comprehensive diagnostic testing, including specific factor inhibitor assays, to guide appropriate treatment. The coexistence of both bleeding and thrombosis in this patient illustrates the paradoxical effects of LA on coagulation, providing valuable insights for clinicians encountering similar cases. © 2024, Amaltea Medical Publishing House. All rights reserved.