Abstract: Background and Objective: An enormous amount of lignocellulosic materials are produced every year throughout the world which can be converted to nutritionally enriched ruminant feed by combination of chemical and biological treatment. This study was undertaken to improve nutritional values of lime treated coconut coir, a lignocellulosic material, by solid-state fermentation with Pleurotus sajor-caju. Methodology: The CaCO3 treated coconut coir was fermented with P. sajor-caju for 56 days at 30°C. Changes of crude protein, lipid, carbohydrate, ash, lignin, cellulose, hemicellulose, reducing sugar, ascorbic acid and carotinoid contents due to fermentation were detected using standard methods. Results: At the end of 56 days fermentation, crude protein, ash and reducing sugar contents were increased by 744.44, 55.61 and 113.80%, respectively. However, crude fiber, lipid, carbohydrate, lignin, cellulose and hemicelluloses contents were decreased by 33.04, 63.42, 20.94, 25.75, 18.57 and 24.42%, respectively. Ascorbic acid and carotenoid were increased by 63.18 and 580.49%, respectively. Conclusion: Thus, bioconversion of coconut coir by P. sajor-caju offers a promising way to convert the lignocellulosic wastes into nutritionally improved animal feed.