The case of a 60-year-old patient who presented with an acute-on-chronic subdural haematoma is reported. Chronic haematoma usually remains asymptomatic, and this is considered to be an unusual course of events. Trivial or minor injury may cause the cortical bridge veins and fragile vessels in the former haematoma to rupture with concomitant reoccurrence of bleeding. Old age, repeated traumatic brain injuries, brain atrophy, antiplatelet agents and oral anticoagulants such as warfarin are considered to be the underlying conditions to cause the reoccurrence of bleeding. However, our patient did not have any of those conditions.