PTP1B phosphatase has become a therapeutic target for the treatment of type 2 diabetes, while recent studies have shown that PTP1B plays a central role in the pathophysiology and development of breast cancer. Phosphatase PTP1B as a new target for oleuropein activity in the MCF-7 model of breast cancer. Here, we have shown that the decrease in PTP1B phosphatase activity after treatment with oleuropein is closely correlated with decreased viability of MCF-7 cells and cell cycle arrest. The purpose of this study was to answer the question of whether PTP1B is a target for oleuropein in MCF-7 breast cancer cells. These results provide new research perspectives on oleuropein and the compound’s potential role in adjuvant treatment of breast cancer. The study used the MCF-7 breast cancer cell model. Before undertaking any natural, integrative or conventional treatment, it is recommended to consult a licensed physician. By providing the information contained in this document, we do not diagnose, treat, cure, mitigate or prevent any type of disease or medical condition. Oleuropein is a natural phenolic compound with anti-cancer activity. Experiments were conducted using cell viability tests, Elisa tests, immunoprecipitation, flow cytometric analysis and computer modeling. More than 500 pages with alternatives and information on natural medicine.