The mistletoe lectins are major active components in the extract of European mistletoe (Viscum album L) that have been widely used in adjuvant chemotherapy of cancer. This study was performed to investigate the antitumor activity of extract of Korean mistletoe (Viscum album var. coloratum) modified with Korean mistletoe lectin (Viscum album var. coloratum agglutinin, VCA). Compared with the results of VCA, survival rate was increased and experimental lung metastasis was reduced by treatment of modified extract (VCM). In addition, the treatment of VCM reduced angiogenesis and VCA-induced toxicity measured by a CAM assay. And VCM inhibited proliferation and induced apoptosis in vitro in tumor cells originated from tissues which are possible to apply topically without surgery. Taken together, the antitumor activities of VCM-treated group outperformed the activities of the VCA-treated group.