Oil palm pressed fibre (PPF) is a lignocellulosic material obtained from processed oil palm fruit. Its usage as energy feed for ruminant is limited by its high lignin content. Ruminants cannot breakdown lignin in the rumen due to the lack of the digestive enzyme, ligninase. Delignifers such as white rot fungi, e.g. Pleurotus tuberregium (Fr. Singer) can be used to significantly degrade lignocellulosic wastes using the solid-state fermentation (SSF) technique. The objective of the study was to determine the chemical composition [Organic matter (OM), Crude protein (CP), Neutral Detergent Fibre (NDF), Acid Detergent Fibre (ADF), hemicellulose, and ash) and in vitro fermentation parameters of raw and biodegraded PPF as well as diets containing them. The PPF materials were biodegraded by inoculating with P. tuberregium (Fr. Singer) spawn for 30 days. In vitro study was conducted with rumen liquor from West African Dwarf (WAD) goats and buffer (ratio 1:2) in 100 mL calibrated syringes containing 200 mg of substrates and gas production was monitored. Biodegradation of PPF with P. tuberregium significantly increased CP content and in vitro dry matter digestibility and decreased hemicellulose but had no effect on NDF. Biodegradation also significantly increased in-vitro DM digestibility but had no effect on NDF and OM digestibility. Optimum DM digestibility was obtained at 40% level of inclusion of biodegraded PFF in the diets vs. 30% for untreated PPF. It is, therefore, concluded that biodegraded PPF can be included up to 40% in WAD goat diets. Further in vivo studies are needed to validate results obtained