Reversible cerebral vasoconstriction syndrome (RCVS) is characterized by acute thunderclap headaches with or without other neurological symptoms, and reversible multi-segmental vasoconstriction of the cerebral arteries. We describe the case of a 49-year-old woman presenting with severe, sudden-onset headaches and multi-segmental vasoconstriction of the cerebral arteries demonstrated on magnetic resonance angiography (MRA). Headaches disappeared within several days, and vasoconstriction of cerebral arteries was markedly improved 6 weeks after the onset. We therefore diagnosed RCVS. In addition to MRA, we repeatedly performed transcranial-color flow imaging (TC-CFI) and transcranial Doppler ultrasonography (TCD) to evaluate cerebral arterial blood flow and risk of cerebral infarction. The first TCD study was performed 6 weeks after the onset; 11 high-intensity transient signals (HITS) were detected in 30 min at the region of vasoconstriction in the right MCA. To the best of our knowledge, this is the first report of HITS-positive RCVS. Ten weeks after the onset, MRA demonstrated disappearance of cerebral arterial vasoconstriction, and TCD detected only 1 HITS in 30 min. Interestingly, TC-CFI still indicated elevated flow velocity in the bilateral MCAs. These findings suggest that TC-CFI may be more sensitive and useful than MRA for diagnosis of RCVS.