Fermented barley extract (FBE) obtained from a barley shochu by-product (shochu kasu) and its ethanol fractions were evaluated as a medium and supplement, respectively, for nisin A production by Lactococcus lactis subsp. lactis ATCC 11454. A Brix 2.5 FBE medium supplemented with glucose provided a high level of nisin A production with a nisin yield comparable to that from a nutritionally rich laboratory medium (basal medium). By adding the ethanol-insoluble (El) fraction of FBE to the basal medium, nisin A production was enhanced concomitant with an increase in bacterial cell growth, while the ethanol-soluble (ES) fraction had a negative effect on nisin A production. These findings indicate that FBE obtained from shochu kasu can be utilized as a preferable medium for nisin A production and could be converted into a value-added food product having preservative functions. The procedure developed in this study would promote recycling of shochu kasu.