Long-term care facility (LTCF) residents are at high risk for infectious diseases, and because of poor implementation of standard precautions, outbreaks frequently occur. We investigated influenza and acute viral gastroenteritis outbreaks in LTCFs to identify effective infection control measures. We investigated 865 LTCFs from the Welfare, Health and Medical Care Information Network database of the Welfare and Medical Service Agency in Japan. We examined the healthcare services provided, the prevalence of infectious diseases, and the occurrence of outbreaks of influenza or acute viral gastroenteritis during 2012. We analyzed the relationships between outbreak occurrence, number of residents affected, and infection control measures used. Influenza and acute viral gastroenteritis outbreaks occurred in 13.6% and 21.6%, respectively, of the LTCFs. Effective influenza outbreak control measures were restricting of symptomatic visitors, moving symptomatic residents to private rooms, and maintaining facilitiesí humidity levels. Measures effective against acute viral gastroenteritis outbreak were using of disposable gloves, facial masks, and gowns when handling vomitus and excreta of persons suspected of infection, monitoring of infections, and staff awareness of infection control measures. To prevent outbreaks, facilities must block the route of infection, maintain room humidity, and regularly train staff in infection prevention and control measures.