Physicochemical characteristics and analysis of functional constituents of mulberry (Morus alba L.) fruit juices were investigated according to four different mulberry cultivars, including iksuppong, daeseongppong, cheongilppong and kwasangppong. Among the four mulberry cultivars examined, the small-sized cheongilppong had higher soluble solid content and lower titratable acidity, whereas the big-sized daeseongppong had higher titratable acidity and lower soluble solid content than other mulberry cultivars. Cheongilppong had higher contents of fructose and glucose, while daeseongppong had higher contents of citric and malic acids than the other mulberry cultivars. Kwasangppong had higher contents of two anthocyanins, cyanidin 3-glucoside and cyanidin 3-rutinoside, while cheongilppong had lower contents of two anthocyanins than the other mulberry cultivars. Daeseongppong had higher contents of resveratrols, flavonoids and moracin, whereas cheongilppong had higher levels of protocatechuic, chlorogenic and caffeic acids than the other mulberry fruits. Of the four mulberry cultivars, daeseongppong and cheongilppong had higher contents of GABA and DNJ, respectively, than the other mulberry cultivars. These results provide useful information to food technologists for the development and standardization of high quality mulberry juices as well as their processed foods.