Seeds such as quinoa, amaranth, chia, and teff are considered as potential sources of plant-based proteins for human consumption. Proteins isolated from pseudocereal grains have the potential to serve as nutritious alternatives to animal-based proteins for various food applications. Quinoa, amaranth, and chia proteins are among the most extensively studied pseudocereal proteins for the characterization of structural, physicochemical, and functional properties. This chapter will review the recent studies on composition, structural characteristics, physicochemical and functional properties of proteins isolated from pseudocereal grains, will discuss several modifications applied for improvement of functional properties and some potential end-product applications.