Flavangenol (FG), an extract of French maritime pine bark (Pinus maritime) mainly contains proanthocyanidin in oligomers. It has many physiological effects, including antioxidant and anti-atherosclerosis. In this study, we evaluated the effects of FG on rat collagen-induced arthritis, a model of human rheumatoid arthritis. The rats were fed with the diet of control, 0.3% FG, or 1% FG for 4 wk after the induction of arthritis. The FG diets, compared with the control diet, suppressed the increase in arthritic score and swelling of the paws in a dose-dependent manner. Histopathological examination revealed evidence that the 1% FG diet suppressed acute and chronic articular lesions in the rats. In addition, the FG diets (0.3% and 1%) suppressed the production of nitric oxide in the plasma of the rats. These results suggest that dietary FG has beneficial effects on collagen-induced arthritis in rats by inhibiting the acute and chronic inflammatory reactions.