Nature is the source of various types of phytochemicals. Some of them are unique chemical compounds only found in certain plants. For example, Cucurbitacin is found in the family Cucurbitaceae. Cucumis melo 'Gama Melon Parfum' (GMP) is a member of the Cucurbitaceae family. Unlike melons in general, GMP melons have a bitter taste. The taste is caused by the high Cucurbitacin content. These compounds are known as anti-cancer. This study aims to identify Cucurbitacin in GMP melons and determine their effects on T47D and MCF7 breast cancer cells. GMP melon fruit medium phase (20DAA) was macerated by methanol and continued by fractionation with chloroform. Cucurbitacin B compounds in the chloroform fraction were identified using HPLC. A cell cytotoxicity test was carried out using an MTT assay with five concentration variations of the chloroform fraction. They were 7.8125, 15,625, 31.25, 62.5, and 125μg/ml. The apoptosis test was carried out using the flow cytometry method with five concentration variations of the chloroform fraction. They were 1, ½, ¼, 1/10, and 1/100 IC50. The results showed that Cucurbitacin B was found in the chloroform fraction with a concentration of 15.69 μg/mL per 1 mg of the chloroform fraction. The IC50 values of T47D and MCF7 cells, respectively, were 98 and 10 μg/ml. The apoptotic test on MCF7 cells showed that at a concentration of 1/100 IC50, the chloroform fraction was able to induce cells to undergo apoptosis.