Rheumatoid arthritis (RA) is a chronic inflammatory disease that is characterized by persistent inflammation in the synovial membranes of joints, migration of activated phagocytes and other leukocytes into synovial and periarticular tissue, erosive damage of articular cartilage and bone. Quercetin (QU) is one of common polyphenolic flavonoid biosynthesized by plants and has been suggested to modulate inflammatory responses in various models. Therefore, we studied the ameliorative effect of QU on collagen induced arthritis (CIA) in wistar rat. The effect of treatment in the rats were monitored by clinical scoring, biochemical parameters, histopathological evaluation and immunohistochemical expression of proteins. Rat with treatment with QU significantly replenished lipidperoxidation (LPO) level, nitric oxide (NO) activity and articular Elastase (ELA) level. It also restored altered enzymatic and non enzymatic antioxidant system of tissue in arthritis rat. Histomorphometric and immunohistochemistry analysis revealed that collagen induced inflammatory cell infiltration ,as well as the elevated expression of NF-B p65 and pro-inflammatory ptotein cyclooxygenase-2 observed in synovial tissue,were significantly inhibited by treatment with QU. The biochemical alterations were further supported by histopathological observations and immunohistochemical expression .we hypothesized that anti-inflammatory activity of QU may be related to predisposition to scavenge free radical, upregulate antioxidant machinery and down regulate immunohistochemical expression of cox2 and NF-Bp65 in arthritis rat.