Corncobs are composed of cellulose, hemicellulose, and lignin. Cellulose and hemicellulose are monomeric sugars that can be utilized as carbon sources for microbial growth and bioproduct formation. However, corncobs present several challenges due to their complex and recalcitrant nature. Addressing these challenges for increased enzymatic and microbial accessibility requires pretreatment methods to break down resistant structures, thus enabling the recovery of fermentable sugars. Different pretreatment methods on corncob wastes have been studied extensively: chemical, physicochemical, and combined pretreatments. Among the developed pretreatment methods, combined pretreatments are the most widely used in the corncob pretreatment process to overcome various limitations in a single pretreatment method. Several combined pretreatment can increase sugar production, shorten processing time and repress inhibitor formation. This review article would assist in determining the best pretreatment method for corncobs according to the advantages, challenges, and effectiveness of various pretreatment methods