Cereal grains have been part of the human diet for centuries. They serve as a source of nutrients and other phytochemicals, including phenolic compounds that may have protective effects against the development of diet-related disorders. Phenolic acids in grains are grouped into derivatives of benzoic and cinnamic acids. They exist in both free and bound forms with an uneven distribution across the kernel. They are concentrated in the outer layers, with the lowest levels in the innermost part of the grain (endosperm). The main phenolic acids in cereal grains are ferulic and p-coumaric acids, largely present as part of the insoluble fractions associated with the cell wall constituents. However, the phenolic composition varies depending on the grain genotype (variety or cultivar), botanical part, growing environment, genotype–environment interactions, milling techniques and method of solvent extraction and analysis. Compared with whole grains, the milled fractions, particularly the outer layers (the bran including the aleurone) and germ, are a concentrated source of phenolic acids and have great potential for use as ingredients in the production of functional foods or the enrichment of other food products.