The effects of ultrasound frequency, acoustic power, and exposure time on the functional properties of whey protein concentrate and sodium caseinate films were examined. Average tensile strength of the ultrasound treated caseinate films was 224% higher than that of the control. The ultrasonic process was more effective on sodium caseinate than whey protein concentrate film. Resistance to puncture was improved for both types of films treated at an acoustic power of 5.22W. Increased exposure time resulted in stronger films. Elongation at break, water vapor permeability, and moisture content of films were not affected by the treatment. Ultrasound showed potential for improving mechanical strengths of milk protein films.