We report an outbreak of norovirus (NoV) which occurred at a military training center in Peru. Thirteen stool samples that were taken from initial cases turned out positive for NoV GII by RT-PCR. A case-control study was performed to determine factors associated with infection.164 probable cases (45.2% clinical attack rate) were identified. The only factor associated with infection was “having shared room with a case” (ORa = 1.7; 95% CI 1.1 to 2.7).Epidemiological findings suggest that the virus was spread person to person. Future investigations of outbreaks of diarrhea in Peru should consider the NoV as an etiologic agent.