Intravascular papillary endothelial hyperplasia (IPEH) is usually a cutaneous lesion thought to represent a peculiar manifestation of an organizing thrombus. The principal significance of IPEH is its microscopic resemblance to angiosarcoma and possible misinterpretation as such. The occurrence of IPEH in the paranasal sinus is exceedingly rare. In this article, we report the first case to our knowledge of IPEH in a vascular lesion that originated from the ethmoid sinus and extended into the sphenoid sinus and sella. Despite the benign nature of this lesion, it could have been mistaken for a malignant tumor because of its clinical course and radiologic findings.