Factor XIII deficiency is a rare inherited bleeding disorder that is often difficult to diagnose. The standard screening tests are normal in these patients and their bleeding phenotype may be variable. We report the case of a 3-year-old girl who presented with an intracranial haemorrhage. Several confounding factors, such as the suspicion of an arteriovenous malformation and the development of a deep venous thrombosis, led to a delay in the diagnosis of factor XIII deficiency. Subsequently, her brother was also found to have severe factor XIII deficiency. This case highlights the importance of a detailed history and of screening families in which index cases have been identified. It should also remind physicians that bleeding disorders may have unusual presentations and should be sought when investigating unexplained bleeding.