Proanthocyanidins (PAs) are a class of oligomeric flavonoids found in a variety of plant foods. Intake of PAs in human diet has been associated with a reduced occurrence of various chronic disorders. Cereal and pseudocereal grains are staple food items. Grain genotypes containing PAs can be developed as functional foods to efficiently improve human health. This review summarises the occurrence of PAs in diverse grains, including rice, wheat, barley, sorghum, millets, buckwheat, and some forage grasses. Great diversity in PA structure and composition has been recorded. The biological activities of the grain PAs, such as antioxidant, antiinflammatory, anticancer, and antidiabetic capacities, are also reviewed. The bioavailability and metabolism of grain PAs in human digestive tract are discussed. Future research directions are suggested on how to improve our understandings of the chemistry of PAs in cereals and pseudocereals and of the biological properties for human health applications.