Sunflower protein isolate was acylated with acetic and succinic anhydride. Succinylation changed the electrophoretic mobility, decreased the lysine and chlorogenic acid content and bulk density, increased the aqueous solubility, shifted the isoelectric point and increased the absorption, emulsification and foaming properties. Acetylation improved the functional properties of the protein to a much lesser extent. Implication of these changes is discussed with reference to food applications.