Internal carotid artery (ICA) dissection is responsible for 10-20% of strokes in young and middle-aged patients. Isolated ICA dissection involving the intrapetrous carotid canal is particularly rare, and no case has been reported to describe an association between intrapetrous ICA dissection and essential thrombocythemia. We report a case of ischemic stroke in the presence of intrapetrous right ICA dissection and essential thrombocythemia. The diagnosis of essential thrombocythemia was performed by bone marrow biopsy. The essential thrombocythemia may cause endothelial dysfunction and predispose to vascular damage such as carotid artery dissection.