Some mechanical and physical properties including total color changes of the cement bonded fiberboard exposed to accelerated weathering process have been investigated. The effects of density, wood fiber/cement ratio and percent accelerator used on physical and mechanical properties of the weathered boards were determined. Comprehensive sets of replicated test data were generated in laboratory conditions and were analyzed statistically. The results obtained in this study were indicative of significant effects of accelerated weathering on physical and mechanical performance of wood fiber based cement bonded fiberboard. Weathering tends to decrease all physical and mechanical properties of the boards measured. Increase of density and percent of accelerators used generally causes an increase in mechanical properties of the boards. It was realized that increase of wood fiber/cement ratio resulted in an increase in modulus of rupture, thickness swelling, and water absorption while a decrease in modulus of elasticity. Percent accelerator used also cause an increase in thickness swelling and water absorption. Total color changes in weathered board were found to be only effected by density of the boards and percent accelerator used.