Enteromorpha compressa seaweeds were evaluated for its in vitro anticancer activity on ovarian cancer cell line. Enteromorpha compressa was collected in and around Mandapam Coast, Rameshwaram, Ramanathapuram District, Tamil Nadu and extracted with 100mL of ethanol using Soxhlet apparatus. The extract showed the presence of phytochemical constituents like alkaloids, saponins, tannins, glycosides, flavonoids, phenols, steroids, terpenoids, quinones and proteins. Total flavonoid content in the chloroform bark extract, using the calibration curve was found to be 1.73mg of quercetin equivalents/g dry weight of the extract. Seaweed extract was subjected to Thin Layer Chromatography for flavonoid detection. The IC50 value of E. compressa extract was found to be 37.68µg/mL against PA1 ovarian cell line compared to the anticancer drug Cisplatin. Hence, the extract may be further analyzed for its potential pharmacological activity against ovarian cancer.