Gac aril contains high level of carotenoids. This carotenoid possesses several pharmacological properties including antioxidant, anti-inflammatory, and anti-tumor activities. To investigate the anti-cancer activity of Gac aril extract on human colorectal cancer cells and its related mechanisms. Colorectal cancer cell lines HCT116 and HT29 were treated with Gac aril extract and its effects on cytotoxicity and anti-proliferation were analyzed using the MTT/MTS and colony formation assay, respectively. Then, further related mechanisms responsible for anti-proliferation were investigated by cell death detection ELISA and Flow cytometry. The results showed that treated cells became rounded up and there was a loss of contact with neighboring cells, leading to a reduction of cell viability. The cytotoxic effects were evaluated IC50 for HCT116 and HT29 cells were 2.16 mg/mL and 1.29 mg/mL, respectively but it not toxic to normal HEK293 at the same dose. Moreover, Gac aril extract significantly inhibits proliferative ability with increasing concentrations having a greater effect. Subsequently, the cellular mechanism responsible for suppressive proliferation was validated. It shows apoptosis induction and arrest of cell cycle. Our findings demonstrated that Gac aril extract can induce apoptosis and arrest of cell cycle at S and G2/M phases in both HCT116 and HT29 colorectal cancer cells.