A Japanese golden eagle, Aquila chrysaetos japonica, was found dead in Nagano Prefecture PB 399-8200, Japan, and subjected to necropsy. The necropsy revealed that the entire length of the intestine was filled with several masses of intestinal parasites. The recovered helminths were identified as one digenean trematode species, Neodiplostomum reflexum; two species of nematodes, Synhimantus sp. and larvae of Porrocaecum sp.; and a single species of Acanthocephala, Centrorhynchus sp. Digenea and acanthocephalans were found in massive numbers, obliterating the intestinal lumen, which suggests that the bird died as a result of the parasitic intestinal obstruction. The same type of helminths as those observed in this case was previously recorded in crested serpent eagles (Spilornis cheela perplexus) in Japan, but the present study emphasizes the presence of the four species in the Japanese golden eagle as a new host record. To the authors' knowledge, this is the first report of N. reflexum in Japan.