This study investigated the physicochemical properties of Pekin duck breast meat obtained from ducks fed diets consisting different types of sipjeondaebo-tang by-products and red ginseng marc with fermented red koji during storage. A total of 180 Pekin ducks (0-day old) were divided into four groups, each consisting of three replicates (15 ducks per pen). This study investigated diets with four types of treatments: control (basal diet),1% blend powder, pelleted 1% blend, and coated pellets of 1% blend; the blend was a mixture of sipjeondaebo-tang by-products powder and red ginseng marc with fermented red koji. There was no significant difference (p>0.05) in duck breast meat pH on storage days 3 and 7, TBARS on storage days 0 through 7, and DPPH radical scavenging on storage days 0 and 7. However, the pH values on storage day 0 and DPPH radical scavenging on storage day 3 were significantly different (p<0.05) in the meats from control and treated diet fed ducks. Especially, on storage day 7, the breast meat from ducks treated with different types of sipjeondaebo-tang by-products and red ginseng marc with fermented red koji showed lower TBARS values and increased DPPH radical scavenging activity compared to the control. In conclusion, addition of different types of sipjeondaebo-tang by-product and red ginseng marc with fermented red koji to 1% blend might be helpful in increasing antioxidant effects and reducing product wastage.