The antioxidant activities of Ulva faciata, Nizimuddinia zanardinii and Gracilaria corticata were investigated in Chabahar, Iran. Methanol extract and n-hexane, dichloromethane and ethylacetate fractions used for antioxidative properties test by the total antioxidative activity, 2,2-diphenyl-1-picryl-hydrazylhydrate (DPPH) free radical scavenging activity, reduction power, metal chelating activity and inhibition of lipid peroxidation methods. The methanolic extracts of three seaweed species showed lower antioxidative properties. The most effective antioxidant properties were observed from the EA fractions of G. corticata and U. faciata. dichloromethane (DCM), fraction of N. zanardinii showed significantly higher total antioxidative activity, DPPH radical scavenging and power reduction in comparison to its n-hexane, EA fractions and crude MeOH extract. There was a strong correlation between the reduction power (r2=0.94) and the total phenolic content of the seaweeds extracts and fractions. The results indicate U. faciata and G. corticata can be potential sources of natural antioxidants and may be efficiently used as nutraceuticals.