Regarding the high prevalence of cancer, research on medicinal plants have been increased due to their availability, cost, and the presence of anticancer compounds. Rorippa nasturtium aquaticum, also called watercress, is a plant from the Brassicaceae family which has large amounts of antioxidants. The present study aimed to examine the antioxidant properties and the phenolic, flavonoid, and anthocyanin contents of the watercress extract and its effect on the growth of cancerous Hela cells, and fibroblasts. Watercress extracts have been prepared through incubation and soxhlet methods in a hydroalcoholic solvent. The phenolic and flavonoid contents of the extract was determined through a spectrophotometric method. Anti-radical activity of the extract was examined by using the radical scavenging activity test of DPPH (2, 2-diphenyl-1 picrylhydrazil). The extract was applied on cancerous Hela cell line and fibroblasts at concentrations varying from 0.625 to 2 mg/ml and cell mortality rates were examined after 24, 48, and 72 h incubation using the MTT test. The extract obtained through the soxhlet method showed more antioxidant activity compared with the incubation method, and had more phenolic and flavonoid compounds. The survival rate of the cancerous Hela cells decreased with time and increasing concentrations of watercress extract. IC50 values after 24, 48 and 72 h were 373, 349, and 333 g/ml, respectively. Based on the results of the study, the soxhlet method is better than the incubation method due to yielding more antioxidant and phenolic compounds. The hydroalcoholic extract of watercress can inhibit the growth of Hella cells and can be considered as an alternative for cervical cancer treatment in the future.