Spinal subdual hematoma (SDH) is an uncommon pathology, and its simultaneous occurrence with cranial SDH is even rarer. We report a unique case of spinal SDH combined with bilateral intracranial SDH, in which the cranial lesion was detected after the evacuation of spinal SDH. The undiagnosed chronic SDH developed acute-on-chronic SDH after the evacuation of spinal SDH. The patient had an uneventful clinical course, and a satisfactory outcome was achieved. The reason for reporting this case is to draw attention to the possibility of concurrent cranial SDH in patients with unexplained spinal SDH. The removal of the spinal SDH may exacerbate intracranial hemorrhage and consequently lead to the potential occurrence of tentorial herniation in patients with accompanied cranial SDH.