Oil palm is currently the world's leading vegetable oil crop, with Indonesia and Malaysia as the two largest producers and exporters of palm oil in the world. In order to meet the demand for palm oil, the mills generate huge quantities of by-products causing an alarming concern on environmental impact. Hence, the effort to transform "waste to gold" is very crucial. This review focused on the extraction methods for holocellulose and lignin, as well as processing methods to produce value-added components such as nanoparticles, fermentable sugar, bioethanol, biochemicals, biofuel and phenolic compounds because the oil palm biomass (OPB) generated contain high amounts of nutritional or bioactive components. Processes such as chemical extractions, enzymatic hydrolysis, microorganism fermentation, organic solvent extractions and green extraction technology using deep eutectic solvents, protic ionic liquid, and supercritical fluid, were used to transform OPB into value-added bio-products for various industries especially food, agricultural, and pharmaceutical industries. Chemical extraction was crucial to extract cellulose and hemicellulose from the lignocellulosic material of OPB prior to other processing methods to produce a variety of valuable components. Sequential mild chemical extraction, cellulase cocktail hydrolysis, supercritical carbon dioxide extraction and ethanol extraction successfully extracted OPB value-added components with improved physical and chemical properties.