The global market is increasingly seeking enhanced dietary options, prompting the food industry to innovate functional components such as plant proteins. This trend signifies a notable shift from traditional reliance on animal proteins towards plant-based sources. Cereal processing, involving grains like wheat, rice, barley, and maize, results in by-products enriched with biofunctional elements, including fiber, proteins, peptides, minerals, vitamins, lignans, phenolic compounds, phytoestrogens, lipids, and more, varying by source type. Notably, cereal by-products, particularly rich in protein from the aleurone layer, offer varied protein compositions between the endosperm and outer grain layer. Particularly, endosperm protein is dominated by glutenins and gliadins, while bran protein contains more albumins and globulins. This review aims to highlight the beneficial effects of proteins and amino acids derived from cereal by-products on human health, underscoring their nutritional significance and potential in disease prevention.