A 55-year-old man suddenly developed anterograde and retrograde amnesia. His colleagues witnessed the onset of the episode and reported that 2 h before the onset of the amnesic attack the patient transiently became pale. Physical examination was unremarkable and neurological examination revealed no focal neurological sign although a laboratory investigation revealed leukocytosis. Pure transient global amnesia (TGA) was diagnosed. The anterograde amnesia resolved 20 h after onset, but the causes of his transient paleness precedent to TGA and leukocytosis were unclear. Thirty-four hours after onset, the patient complained of sudden back pain and radiological studies revealed aortic dissection (AD; Stanford type B). We emphasize AD as a rare cause of pure TGA, because TGA in itself often has a benign natural history, but AD can be life-threatening if undiagnosed. The precedent pain, transient systemic symptoms, and leukocytosis can be red flags suggesting AD as an etiology of TGA.