Objective: To evaluate antitumor activities of Fritillaria imperialis and Eryngium caucasicum methanolic extracts on human hepatoma (HepG2) and colon cancer (HCT116) cell lines in comparison to human foreskin fibroblasts as the normal cells. Methods: Methanolic extracts of Fritillaria imperialis and Eryngium caucasicum were prepared by the maceration method. The effect of the extracts at various concentrations (100, 200, 400, 600, and 800 μg/mL) on cell survival was evaluated using the MTT method. Besides, fluorescence staining was used to evaluate death patterns of the cells. Results: MTT assay showed that Fritillaria imperialis significantly decreased the viability of all cell lines after 24 and 48 hours of treatments. However, Eryngium caucasicum extract did not show any significant cytotoxicity effect on the cell lines. Fluorescence staining revealed that Fritillaria imperialis induced apoptosis of HCT116 cells at 550 μg/mL. Conclusions: Fritillaria imperialis extract has antiproliferative and cytotoxic effects on HCT116 and HepG2 cancer cells and therefore, may serve as an anticancer agent.