Based on our previous studies on cytotoxic potentials of Polygonum hydropiper L, two steroidal compounds beta-sitosterol and stigmasterol were isolated from the most active fraction and were subjected to cell lines cytotoxicity. Isolated compounds were tested against HeLa, MCF-7 and NIH/3T3 cell lines following MTT assay. Furthermore, the compounds were also docked against tyrosine kinase enzyme to predict the binding mode of phytosterols in the active sites of the enzyme. Beta-sitosterol exhibited considerable cytotoxicity against NIH/3T3, HeLa and MCF-7 cell with 67.05 ± 2.08, 79.63 ± 2.34 and 71.50 ± 1.57% lethality respectively at 1 mg/ml concentration. Median inhibitory concentrations calculated from dose response curve against NIH/3T3, HeLa and MCF-7 cells were 440, 170 and 200 µg/ml respectively. Stigmasterol was more effective against MCF-7 and NIH/3T3 cells by killing 87.50 and 81.45% cancerous cells respectively at 1 mg/ml concentration. Stigmasterol showed 77.25% cyctotoxicity against HeLA cells at 1 mg/ml concentration in MTT assay. The IC values for HeLA, MCF-7 and NIH/3T3 cells were 170, 60 and 140 µg/ml respectively. In docking studies, the docking score for beta-sitosterol and stigmasterol were -7.266 and -4.89 respectively. The binding energies for beta-sitosterol and stigmasterol were -41.21 and -41.04 respectively. Such lower binding energies indicate that the compounds fit into the active site more strongly. Binding affinities for both compounds were -7.76 and -7.68 respectively. Both phytosterols possess significant anticancer potentials and can be effective in the prevention and treatment of several malignancies.