The coral crab Fungicola fagei (Decapoda: Brachyura: Cryptochiridae) is recorded for the first time from the Hawaiian Islands, where it was discovered in a previously unknown association with the solitary, free-living mushroom coral Lobactis scutaria (Anthozoa: Scleractinia: Fungiidae). The associated crab species was discovered off Hilo on the island of Hawai‘i, where it appeared to be relatively common. It could have been previously overlooked because of its small size (max. ca. 1 cm long) and its hidden life style inside the host coral. Species identification is based on the morphology of the carapace and use of the cytochrome oxidase subunit I (COI) barcode gene as molecular marker. Fungicola fagei is known from other localities in the Indo-West Pacific region, where it is only hosted by mushroom coral species of the genera Podabacia and Sandalolitha. The record of F. fagei from the Hawaiian Islands represents a northeastward extension of its known geographical distribution range, 6,000 km away from its nearest locality in Vanuatu, despite the availability of host species as eastward as the Cook Islands and French Polynesia. Because these other host species do not occur in the Hawaiian Islands, F. fagei's occurrence here is only possible because of its association with L. scutaria, uniquely recorded from Hawai‘i.