Sulfated polysaccharides were isolated from green seaweed Codium tomentosum by using two different extraction processes: Hot water extraction (HEP) and Ultrasound Enhanced Extraction (UEP). The yield, chemical composition and antioxidant activity of isolated polysaccharides were determined and compared. In present study, the ultrasound-enhanced extraction method influenced a usual yield and extraction time. It increases the yield up to 16.2% in 45 min from 12.35% in 5 h of hot water extraction yield. The chemical composition of UEP was also significantly affected and showed higher sulfate and uronic acids content. Both samples presented comparable good antioxidant activities on hydrogen peroxide, nitric oxide, ABTS, DPPH, deoxyribose radicals. However the UEP exhibited higher antioxidant potential than HEP. The IR spectra of both sulfated polysaccharides revealed characteristic absorption bands. It shows the presence of hydroxyl, carboxyl and sulfate groups. This study revealed that chemical composition and antioxidant activity of polysaccharides obtained from Codium tomentosum vary according to the process for their extraction. Moreover, sulfated polysaccharides obtained by UEP or HEP both can be a good source of natural antioxidants and can be harnessed for further biotechnological applications.