Pleurotus species include edible mushrooms that grow on a range of lignocellulosic substrates by secreting hydrolytic and oxidative enzymes. This flexibility offers opportunities to valorize agro-industrial residues for sustainable production of food and biomaterials. In this study, we analyzed the genome of Pleurotus pulmonarius and its biocatalytic potential for lignocellulose saccharification using proteomics and biochemical assays. The fungus was cultivated on beechwood, corn stover, and xylose. Beechwood induced the richest secretome with abundant oxidases. The corn stover secretome had fewer proteins but was focused on carbohydrate-acting enzymes, with abundant polysaccharide-degrading and accessory enzymes. Despite lower enzyme diversity, corn stover secretome achieved higher lignocellulose saccharification, further improved by oxidoreductase inhibition. Supplementing an industrial cellulase cocktail with P. pulmonarius corn stover secretomes enhanced sugar release by 40%. These findings highlight the dynamic enzymatic response of P. pulmonarius to lignocellulosic substrates and its potential in biomass valorization and the design of enzymatic cocktails.