A nano-sized double-walled carrier composed of chitosan and β-lactoglobulin (β-Lg) for oral administration of epigallocatechin gallate (EGCG) was developed to achieve a prolonged release of EGCG in the gastrointestinal tract. Carboxymethyl chitosan (CMC) solution was added dropwise to chitosan hydrochloride (CHC) containing EGCG to form a primary coating by ionic complexation. Subsequently, β-Lg was added to create a secondary layer by ionic gelation. The obtained EGCG-loaded chitosan/β-Lg nanoparticles had sizes between 100 and 500 nm and zeta potentials ranging from 10 to 35mV. FT-IR spectroscopy revealed a high number of hydrogen-bonding sites in the nanoparticles, which could incorporate EGCG, resulting in high encapsulation efficiency. EGCG incorporated in the primary coating was released slowly over time by diffusion from the swollen CMC-CHC matrix after the outer layer of β-Lg was degraded in the intestinal fluid. The sustained-release property makes chitosan/β-Lg nanoparticles an attractive candidate for effective delivery of EGCG.