OBJECTIVES:: Rheumatoid arthritis is a chronic relapsing autoimmune disorder with multifactorial etiology and prognosis. Chronic use of current therapies has many side effects of the GIT, cardiovascular system and kidneys. The need for a drug, which can be used chronically with minimal side effects, is still unmet. Hence the objective of the present investigation was to study the anti-arthritic activity of the morin in adjuvant-induced established polyarthritis in rats. METHODS:: Polyarthritis was induced in female Wistar rats using Freund’s Complete Adjuvant (FCA) and the established procedure, except that the injection was given in the tail instead of the paw. Leflunomide (10 mg/Kg) was used as standard and morin was used in three doses (10, 30 and 100 mg/kg, p.o.) were administered orally daily for 28 days. RESULTS:: Morin (30 and 100 mg/kg, p.o.) treatment showed a significant inhibition (p < 0.05) in FCA-induced alterations in body weight, food and water intake, paw volume and percent inhibition. Mechano-tactile allodynia, thermal analgesia, and mechanical analgesia threshold were significantly improved (p < 0.05) by morin (30 and 100 mg/kg, p.o.) treatment. C-reactive protein, erythrocyte sedimentation rate and Tumor necrosis factor-alpha (TNFα) levels were significantly decreased (p < 0.05) while serum turbidity was significantly increased (p < 0.05) after morin (30 and 100 mg/kg, p.o.) treatment. Histopathology evaluation of paw tissue from morin treated rats showed reduced synovitis, panus and oedema. CONCLUSIONS:: Morin showed promising curative properties against FCA induced established polyarthritis in rats through multiple mechanisms and can be considered as a potential agent for further development.