The present study evaluated the anti-inflammatory and antioxidant potential of alginic acid isolated from brown algae Sargassum wightii in arthritic rats. Arthritis was induced in male Sprague-Dawley rats by intradermal injection of complete Freund's adjuvant into the right hind paw, produce inflammation of the joint tissue. Paw edema volume, enzymes linked to inflammation such as cyclooxygenase, lipoxygenase and myeloperoxidase, and the level of ceruloplasmin, C-reactive protein and rheumatoid factor were evaluated in all the experimental groups. Oxidative stress during inflammation was analyzed by estimating lipid peroxidation and the activities of antioxidant enzymes such as superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and non-enzymatic antioxidant, reduced glutathione. Alginic acid treatment (100 mg/kg) in arthritic rats exhibited reduced paw edema volume along with reduced activities of enzymes such as cyclooxygenase, lipoxygenase and myeloperoxidase. Reduction in the level of C-reactive protein, ceruloplasmin and rheumatoid factor were also observed in arthritic rats treated with alginic acid along with reduced lipid peroxidation and enhanced activities of antioxidant enzymes, which suggest the antioxidant potential of the compound. Histopathological analysis of paw tissue showed that alginic acid treatment reduced paw edema and inflammatory infiltration in arthritic rats. Overall results suggest that alginic acid isolated from Sargassum wightii exhibits potent anti-inflammatory and antioxidant activity, and can develop this marine alga as an alternative source for therapy and can be used as a drug candidate for the development of anti-inflammatory agent.