This study describes how the rheological properties of colloidal dispersions formed by heteroaggregation of oppositely charged protein-coated lipid droplets depend on total particle concentration. Mixed-particle emulsions were formed by mixing single-particle emulsions containing either β-lactoglobulin-coated lipid droplets (ζ≈-42 mV, d(43)≈ 0.35 μm) or lactoferrin (LF)-coated lipid droplets (ζ≈+26 mV, d(43)≈ 0.32 μm). A series of single-particle and mixed-particle emulsions with different total fat contents (5% to 40%) were prepared, and their mean particle size, apparent viscosity, and shear modulus were measured. Mixed-particle emulsions (40% LF: 60%β-Lg) containing relatively high fat contents (>10%) had high viscosities and paste-like properties. These rheological characteristics were attributed to extensive particle aggregation and network formation due to electrostatic attraction between oppositely charged droplets. The viscosities of mixed-particle emulsions were much higher than those of single-particle emulsions with equivalent fat contents. Measurements of the color coordinates (L*, a*, b*) of mixed-particle emulsions with low fat contents showed that they had similar appearances as single-particle emulsions with high fat contents. This study has important implications for the creation of reduced fat foods with similar sensory qualities as higher fat foods.