Adult nematode parasites were recovered from the heart blood of a deceased island fox (Urocyon littoralis) submitted for necropsy to determine the cause of death. Examination of the recovered nematodes supported the generic diagnosis of Angiocaulus, a parasite in Angiostrongylidae found in domestic and wild canids and mustelids. Specific diagnosis of the worms from the island fox as Angiocaulus gubernaculatus is based on the morphology of the dorsal ray in the copulatory bursa of the male worm and its comparison with published descriptions of Angiocaulus raillieti and A. gubernaculatus. Although A. gubernaculatus has been typically associated with mustelid hosts, its occurrence in the island fox indicates that the host distribution for the parasite may not be as restricted as previously believed.