This research investigated the quality properties of yogurts added to barley (1, 2, and 3%) and tagatose or sucrose. After inoculation of S. thermophilus, pH, titratable acidity (TA), viscosity, and viable cell count were measured at 4 h intervals for 16 h and color value, antioxidant activity, and sensory evaluation were determined after fermentation in triplicate. In the case of yogurt containing only tagatose or sucrose, the pH was hardly decreased, but when 2-3% barley was added, the pH reached below 4.5 before 16 h. In addition, TA and viscosity tended to increase as barely was added. Viable cell count increased slowly in yogurt with tagatose, but rapidly increased when barley was added. As barley content increased, yellowness, redness, and antioxidant activity tended to increase, and significantly higher antioxidant activity in barley tagatose yogurt. Sour strength increased and significant difference in the sweetness was not observed when barley amount increased. Although there was no significant difference in overall acceptability, tagatose yogurt containing 3% barley scored the highest in preference. In conclusion, the fermentation rate of yogurt inhibited by the addition of tagatose is improved by the addition of barley, and the growth rate of lactic acid bacteria is considered to play a role.