Lignocellulosic biomass is a renewable material of great abundance. However, its recalcitrant characteristic requires the application of pretreatments. Sugarcane bagasse (SB), soybean hulls (SH), cocoa pod husks (CPH) and oil palm empty fruit bunches (OPEFB) were subjected to imidazole pretreatment in order to evaluate chemical composition variations and influence over enzymatic hydrolysis efficiency. Non-treated SH, SB and OPEFB have higher content of holocellulose, while CPH is rich in lignin polymers (31.2%). After imidazole-pretreatment, all biomasses presented structural disorganization of lignocellulosic fibres and enrichment in the percentage of cellulose. Levels of up to 72% delignification were obtained, which allowed an enzymatic conversion greater than 95% for SB, SH and OPEFB, while only 83% was reached for CPH. Imidazole is then emerging as a potential catalyst for the pretreatment of agro-industrial by-products, allowing the valorisation of these residues and their reinsertion into the production chain under a biorefinery concept.