Four viruses showing cytopathic effects in MDBK cells were isolated from brains of cattle showing downer cattle syndrome in 2012. The isolates were confirmed to belong to the genus Rubulavirus of the subfamily Paramyxovirinae. Isolate QIA-B1201 had the ability to hemagglutinate red blood cells from several species of animals and was capable of adsorbing guinea pig erythrocytes on the surface of infected Vero cells. Nucleotide sequence analysis showed that two isolates (QIA-B1201 and QIA-B1204) had high similarity with other human and animal PIV5 isolates ranging from 98.1 to 99.8%. The highest sequence similarity of the two isolates corresponded to strain KNU-11 (99.8% at the nucleotide and amino acid level) isolated from suckling piglets in Korea in 2012. To evaluate the virulence of strain QIA-B1201, we inoculated bPIV5 into 5 week-old mice via both the intraperitoneal and intracranial route. Body weight was not significantly altered in mice inoculated with QIA-B1201. In this study, we isolated and characterized novel bPIV5s from brain samples showing downer cattle syndrome, but were not able to elucidate the pathogenicity of the bPIV5s in mice.