Mango leaf tea has been traditionally used by different cultures to reduce inflammation in the body. There is evidence that chronic inflammation increases the risk of cancer. This study investigates the antitumoural effects of pressurized mango leaf extracts on minimally (MCF7) and highly invasive (MDA-MB-231) breast cancer cells as well as on non-tumourigenic cells (MCF10). Extracts showed protective properties against oxidation and cytotoxic effects against breast cancer cell lines, causing minor damage to non-carcinogenic cells. Nonetheless, some selective activity, depending on hormone receptor status, was observed. This was possibly related to the presence of minor compounds. Extracts with high levels of gallotannins showed cytotoxic action against MCF7 cells, while those which had methyl gallate and homomangiferin as common components were more effective against MDA-MB-231 cells. Therefore, the cytotoxic effect of mango leaf extracts might be attributed to the synergistic effect of different polyphenols and not just to mangiferin on its own as the predominant compound in mango leaves.