This study aimed to evaluate the antioxidative potential and antimicrobial activity of eleven seaweeds, including Sargassum ilicifolium, Sargassum tenerrimum, Stoechospermum marginatum, Padina tetrastromatica, Dictyota maxima, Gracilaria corticata, Acanthophora spicifera, Batrachospermum sp., Caulerpa peltata, Chaetomorpha crassa, Ulva lactuca. Sargassum ilicifolium, Sargassum cinereum, and Sargassum tenerrimum were studied for anticanser activity. Seaweed extracts were screened for their antimicrobial activity against the following pathogens: Klebsiella, Bacillus thrungenis, Psudeomonus sp < em>., and Streptococcus aureus. Antimicrobial activity was measured using ELISA microplate reader. In ethanol extract, Sargassum tenerrimum and Caulerpa peltata exhibited maximum inhibition on the growth of the tested Klebsiella species. The antioxidant potential of various seaweed extracts was determined using the DPPH and FRAP. In the present study, the DPPH activity was consistently higher in the methanolic extracts of Phaeophyta. The maximum percentage of radical-scavenging activity was observed in the Padina tetrastromatica. This study was designed to assay the cytotoxic activity of the extract from brown alga; namely, Sargassum ilicifolium, Sargassum cinereum and Sargassum tenerrimum against breast cancer cells MCF7 by using MTT assay. The research was performed as an in vitro study. The Sargassum cinereum showed the highest IC50 value compared to Sargassum ilicifolium and Sargassum tenerrimum. The seaweed extract can be used as promising anti-oxidative agents, anti-microbial and anti-cancerous in cosmeceutical or nutraceutical products which can upturn the value of an otherwise worthless weed.