Barley is the basic raw material for brewing. Its chemical composition, brewing, and technological indices are highly determinative for the beer quality and the economical efficiency of the brewing process. Barley is rich in protein, carbohydrates, dietary fibers, minerals, and vitamins. The presence of nonstarch polysaccharides as mixed linkage (1-3),(1-4)-␤-D-glucans and arabinoxylans together with the enzymes are responsible for barley modification. Malting is a complex process that involves many enzymes; important ones are ␣-amylase, ␤-amylase, ␣-glucosidase, and limit dextrinase. During the process of malting and brewing, the by-products left after separation of the wort are rich in protein, fibers, arabinoxylans, and ␤-glucan. This review summarizes and integrates barley grain with respect to nutritional, functional, and compositional changes that take place during malting and brewing. It also explores in-depth the several by-products obtained after brewing and their potential for various food applications. Barley brewing by-products offer an opportunity for cereal-based baked and extruded products with acceptable sensory and nutritional characteristics.