Sapoviruses (SaVs) belong to the Caliciviridae family and can cause gastroenteritis in humans and swine. Despite extensive testing, human sapoviruses have been found only in sporadic cases and in one mixed outbreak in children between 1994 and 2007 in the Netherlands. Here we describe a change in sapovirus epidemiology in the Netherlands resulting in sapovirus outbreaks and infections in adults. From November 2007 to January 2009, 478 outbreaks of acute gastroenteritis were reported to the National Institute for Public Health and the Environment in the Netherlands as a part of ongoing surveillance. Sapoviruses were found to be the most likely cause of 19 outbreaks (4%). During the same 2-year period, sapovirus infections were reported in Sweden, Slovenia, and Hungary. In the Netherlands, further characterization of outbreak strains showed that 12 (63%) sapovirus outbreaks were caused by genotype I.2 viruses. Most patients were adults older than 60 years (range, 1 to 100 years). Phylogenetic analysis using all presently available SaV sequences showed high homology between genotype I.2 strains detected in different geographical regions (Sweden, Slovenia, Taiwan, Japan, and Russia) since 2007. These first reported outbreaks of sapovirus infections in adults in the Netherlands were remarkable. Detection of identical genotypes in many samples might suggest that these viruses have the same origin, and since the infection is spreading fast, the prevalence of sapovirus infection may be increasing. The incidence of sapovirus infections in these countries suggests that a substantial part of Europe is affected by this virus.