Norovirus (NoV) and sapovirus (SaV) are important pathogens of human gastroenteritis. Compared to NoV, the transmission route of SaV is unclear. An outbreak of gastroenteritis occurred at a restaurant in June 2008, and SaV and NoV were detected in fecal specimens from 17 people who ate at the restaurant and one asymptomatic food handler and also in stripped shellfish and liquids remaining in the shellfish packages by reverse transcription-polymerase chain reaction (RT-PCR) and/or real-time RT-PCR. Nucleotide sequencing analysis of the RT-PCR products corresponding to the partial capsid region revealed 99.3–100% identities for SaV and 98.6–99.3% identities for NoV among the digestive diverticulum of the frozen stripped shellfish (Ruditapes philippinarum), “Asari,” the package liquid, and feces from symptomatic or asymptomatic guests. These results suggested a link between the consumption of contaminated shellfish and clinical features in the patients. While the transmission of NoV by shellfish has been reported, this report shows that SaV can also be transmitted by shellfish. J. Med. Virol. 82: 1247–1254, 2010. © 2010 Wiley-Liss, Inc.