A Gram-staining-positive, coccus-shaped, non-spore-forming, facultatively anaerobic bacterium, designated AC-1(T), was isolated from an acidogenic fermentation bioreactor treating food wastewater. On the basis of 16S rRNA gene sequence analysis, strain AC-1(T) was shown to belong to the genus Vagococcus. The closest phylogenetic relatives were Vagococcus elongatus PPC9(T) (97.4 % 16S rRNA gene sequence similarity), Vagococcus penaei CD276(T) (96.7 %) and Vagococcus carniphilus ATCC BAA-640(T) (96.6 %). The major fatty acids were C(18 : 1)ω9c (24.8 %) and C(16 : 0) (19.5 %) and the G+C content of genomic DNA was 44.2 mol%, which supported the affiliation of strain AC-1(T) to the genus Vagococcus. Strain AC-1(T) and V. elongatus DSM 21480(T) exhibited 11 % DNA-DNA relatedness. Physiological and biochemical tests differentiated strain AC-1(T) from the type strains of recognized species of the genus Vagococcus. Therefore, strain AC-1(T) is considered to represent a novel species, for which the name Vagococcus acidifermentans sp. nov. is proposed. The type strain is AC-1(T) ( = KCTC 13418(T) = LMG 24798(T)).