Ultrasonic treatments can be used to enhance protein extraction yields from foods. The objective of this work was to determine how the treatment of oat brans with ultrasounds affects the functionality and the physical properties of the hydrolyzed proteins. Oat brans were treated with ultrasonic cleaner bath and high-powered ultrasonication, after which, the proteins were extracted and hydrolyzed using three different proteases (Flavourzyme, Papain, and Alcalase). The effect of ultrasonication of brans had a minimal effect on the secondary structure, free thiol, zeta potential, and hydrophobicity of hydrolysates. Ultrasonic treatments did cause the release of two proteins not found in the control, specifically vromindoline and tryptophanin. The hydrolysis of protein isolates with proteases produced hydrolysates with notable antidiabetic activity (DPP-4 and alpha-amylase inhibition) but this was not influenced by the difference in polypeptide compositions.