Food proteins have been widely used as carrier materials for the encapsulation and protection of bioactive molecules. Clarification of the mechanism of protein–bioactive molecule interaction is important for the development of protein-based carrier systems. The interaction of b -casein with resveratrol, a natural polyphenol, was studied using ultraviolet–visible absorption and fluorescence spectroscopy. It was found that the interaction shifted the protein fluorophores to a more hydrophilic environment and the polyphenol to a more hydrophobic environment. The formation of the complex with b -casein did not affect trans – cis isomerization of resveratrol or the total antioxidant activity of the protein–polyphenol system, as analyzed respectively using spectrophotometry and the 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) assay. The protective effect of resveratrol against photodecomposition of folic acid was not affected by binding to b -casein. The data obtained should provide insight into protein–polyphenol interaction mechanisms and aid the development of b -casein-based carrier systems for the delivery of bioactive molecules.