Grape seed (GS) oil is one of the potential functional foods. For the first time, we evaluated the therapeutic effects of GS oil saponifiable (Sap)-fraction from black (BSap) and green (GSap) grapes on MCF-7 cells and Ehrlich ascites carcinoma (EAC) in mice. The fatty acid composition of BSap and GSap was determined using gas chromatography-mass spectrometry analysis. Approximately twelve distinct fatty acids were detected in BSap and eleven in GSap. BSap showed a greater cytotoxic effect on MCF-7 cells than GSap did by inducing apoptosis and reducing inflammation, while both grape fractions had superior potency to 5-FU. Furthermore, BSap massively boosted apoptosis and lowered redox potential (E_h) and CD44⁺ cells in EAC cells of EAC-bearing mice more than GSap, and both fractions were more efficient than 5-FU. Blood tests and liver histopathology revealed significant improvement in EAC-induced pathological alterations with these fractions. The in silico analysis implied the competitive inhibitory impacts of the most abundant fatty acid composites in BSap and GSap on cancer-metastasis-associated proteases (cathepsin B and MMP9). Also, this analysis predicted that the apoptotic action of these Sap fractions is independent of the 5ˈAMP-activated protein kinase. Therefore, grape Sap-fraction, especially BSap, may be a useful agent for cancer prevention.