Haemophilia is an inherited X-linked bleeding disorder characterised by a deficiency or absence of clotting factor VIII (haemophilia A) or IX (haemophilia B), which can cause musculoskeletal bleeding. The standard treatment for haemophilia is with factor concentrates to replace the missing or deficient clotting factor. However, there is a risk that the immune system develops antibodies against the exogenous factor, known as inhibitors. Managing patients with haemophilia and inhibitors who develop bleeding in unusual sites can be challenging for the treating physician. Here, we present a rare case of patient with severe haemophilia A who was diagnosed with inhibitors after developing bleeding in the left posterior chest wall (extra pleural haematoma). The patient was successfully managed with activated prothrombin complex concentrate (aPCC) (FEIBA: FVIII inhibitor bypassing activity; Baxter AG), and the pain and swelling gradually resolved over three weeks. This case emphasises the importance of clinical suspicion of inhibitor formation in a patient already diagnosed with haemophilia A presenting with unusual bleeding that does not respond to standard treatment.