This study first used adzuki bean seed coat polyphenol (ABSCP) to modify zein and form covalent nanoparticles (ZAP) and used ZAP as an emulsifier to stabilize Pickering emulsion (ZAE). The results showed that the ratio of zein-ABSCP controlled the physicochemical properties of the two compounds. ZAP could be absorbed on the water–oil surface and stabilized ZAE, which presented as a non-Newtonian fluid state with good rheological properties. The addition of ABSCP inhibited lipid oxidation in a dose-dependent manner, as verified through the analysis of accelerated oxidation experiments (50 °C, 20 days). In in vitro gastrointestinal digestion of ZAE showed that free fatty acids (FFA) release gradually decreased with ABSCP concentration increasing. Moreover, ABSCP gave ZAE a strong red–yellow color, which allowed ZAE to be used for specific applications (e.g., natural pigments). Our findings make it feasible to develope functional food and food-grade delivery systems made of protein-plant polyphenols nanoparticles.