In this study, soy protein isolate (SPI) dispersions (3%, w/v) were treated with hydrodynamic cavitation (HC) with a venturi tube (treatment volume: 2 L) and ultrasonic cavitation (UC) (treatment volume: 200 mL and 2 L) under the power of 550 W for 5, 10, 20, and 30 min. The effects of HC and UC treatment on the physicochemical and functional properties of SPI were investigated, and the results were compared to better evaluate the HC effects on food proteins. The results showed that the electrophoretic profile and pH were not affected by UC or HC treatment. The particle size and viscosity of SPI were reduced after UC or HC treatment. Both UC and HC treatment significantly (P < 0.05) increased the surface hydrophobicity. UC treatment at the volume of 2 L did not alter the exposed or total sulfhydryl content; however, UC treatment at the volume of 200 mL and HC treatment altered the exposed sulfhydryl content and decreased the total sulfhydryl content. Moreover, the solubility, emulsifying activity index, emulsion stability index, and foaming capacity were also significantly (P < 0.05) improved; however, foam stability was reduced after UC and HC treatment. Under the conditions investigated in this study, the effect of HC treatment on the physicochemical and functional properties of SPI was more pronounced than that of UC treatment at the volume of 2 L, and was similar to that of UC treatment at the volume of 200 mL. These results suggest that HC could be an effective method to improve the functional properties of food proteins. •The effects of hydrodynamic and ultrasonic cavitation on soy protein isolate were compared.•The particle size and viscosity were reduced after treatment.•The surface hydrophobicity and solubility were increased after treatment.•Some functional properties were improved after treatment.•The effect of hydrodynamic cavitation was more pronounced than that of ultrasonic cavitation at large volume.