The stabilizing behaviour of soluble soy polysaccharide (SSPS) on acidified dispersions of soy protein isolate (SPI) and SPI-stabilized emulsions was studied. SPI and SSPS suspensions were characterized via light scattering, surface charge measurement, turbidity, sedimentation analysis, and light microscopy. At acidic pH (pH 6-3), it was found the addition of at least 0.25 wt% SSPS was required to stabilize 0.75 wt% SPI suspensions against aggregation and phase separation, likely via steric repulsion. The mechanism of SPI-SSPS interaction was shown to be electrostatic in nature by testing the effects of increased ionic strength of the suspensions. The stabilizing effect of SSPS on SPI was then applied to 5% oil-in-water emulsions. The presence of SSPS stabilized the emulsions against droplet size increases and phase separation over time. Overall, the results demonstrated that it was possible for SSPS to stabilize SPI suspensions and that SPI-SSPS interactions may be used as a tool to stabilize O/W emulsions.