Abstract: Whey protein isolate (WPI) and sugar beet pectin (SBP) were grafted based on dry heating Maillard reaction. The effects of the protein-to-polysaccharide ratio and reaction time on the grafting degree and functional properties of the conjugates were investigated. Peppermint oil nanoemulsions were subsequently prepared using the resulting conjugates. The results showed that the WPI-SBP conjugates prepared at a mass ratio of 1:1 and reacted at 60 °C for 2 days exhibited a grafting degree of 26.77%, along with the highest emulsifying activity (14.24 m²/g) and emulsion stability (117.13 min). A comparative study on the properties of peppermint oil nanoemulsions prepared with WPI, a WPI/SBP physical mixture, and WPI-SBP conjugates revealed that emulsion prepared from WPI-SBP conjugates showed the smallest particle size of 60.68 nm and polydispersity index of 0.214, as well as the lowest creaming index of 27%, indicating that the physical stability and functionality of the emulsion were significantly improved.