Currently, murine noroviruses (MNV) are the most prevalent viral pathogens identified in laboratory animal facilities. While several reports exist concerning the prevalence of MNV in North American research facilities, very few reports are available for other parts of the world, including Korea. This study evaluated the prevalence of MNV infection in 745 murine sera collected from 15 animal facilities in Korea by enzyme linked immunosorbent assay (ELISA). Positive cases were subcategorized by murine strain/genetics, housing environments and animal sources. In summary, 6.6% of inbred/outbred mice purchased from commercial vendors were seropositive, 9.6% of in-house colonies were seropositive and 27.0% of genetically modified mice (GMM) were seropositive. Partial gene amplification of fecal isolates from infected animals showed that they were homologous (100%) with MNV-4.