Viscum album var. coloratum (Korean mistletoe; KM) is an herbal medicine that is used worldwide for the treatment of various immunological disorders and cancers. KM extract showed enhanced anti-oxidative effects in 2,2-diphenyl-1-picrylhydrazyl, Trolox equivalent antioxidant capacity, and 5-(and-6)-chloromethyl-2′,7′-dichlorodihydrofluorescein diacetate acetyl ester assays after being fermented with a crude enzyme extract from a soybean paste fungus, Aspergillus kawachii. High-performance liquid chromatography analysis showed four increased peaks in enzyme treated KM. The increased peaks were isolated and identified as caffeic acid (1), hesperetin (2), syringaldehyde (3), and lyoniresinol (4). Among the four compounds, only 1 and 4 showed strong anti-oxidative activity. Therefore, the fermentation increased the contents of 1 and 4, which consequently increased the anti-oxidative activity of KM.