Background: Pergularia tomentosa is a member of the Apocynaceae family found in a wide geographical region including the Gulf region, North Africa and the Middle East. It is known as Fattaka, Ghalqa or Am Lebina in Saudi Arabia, It is used as a remedy for the treatment of skin sores, asthma, and bronchitis. Objective: This study aims to investigate the cytotoxic effects of methanolic extract and Latex (milky secretion) extract. Methods: The stem of Pergularia tomentosa was cut, air dried and soaked for 72 h with methanol repeatedly three times. The crude latex (milk extract) was collected from healthy stem parts of P. tomentosa L by cutting the petiole of leaves, and left to flow where a thick white liquid (Milky) were secreted, collected in amber glass tube and extracted with methanol. Further, the methanolic extract was fractionated by subsequent extraction with various solvents, viz. n-hexane, ethyl acetate and methanol. The cytotoxic effects of Pergularia tomentosa L were evaluated using three cancer cell lines of colon carcinoma (HCT-116), hepatocellular carcinoma (HepG2) and breast carcinoma (MCF-7). The cytotoxic effects of Pergularia tomentosa L extracts against HCT-116, HepG2, and MCF-7 were determined by crystal violet staining method. Results: The potency of plant extract to decrease the cell viability of human cancer cells was arranged in descending order as follows: Methanol extract (IC50 = 10.2 μg/ml, 13.6 μg/ml and 29.5μg/ml, respectively). > Milky secretion extract (IC50 = 52.6 μg/ml, 58.6 μg/ml and 120 µg/ml, respectively). Methanolic extract was strong cytotoxic activity against HCT-116 and HepG2 (IC50= 10.2, 13.6 µg/ml, respectively) and moderately activity against MCF-7 (IC50= 29.5 µg/ml). The Milky extract exhibited moderate activity against HCT-116 and HepG2 (IC50= 52.6-58.6 µg/ ml, respectively) and weak activity against MCF-7 (120.0 µg/ml). Conclusion: The methanol extract of Pergularia tomentosa L showed higher cytotoxic effect as compared to the Latex (Milky secretion) extract. These extracts can be used as natural antitumor. In Future modern chromatographic separations are needed to get more quantity of metabolites. Further detailed investigation of the isolated metabolites is required to identify the phytoconstituents responsible for antioxidant and cytotoxic effects.