We present a comprehensive study of the photo-induced phase transition of azobenzene-containing poly(N-isopropylacrylamide) (PNIPAM) in block copolymers (BCPs) upon the isomerization of azobenzene in the mixed solvent of water and dioxane. The BCP is composed of a poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) block and a PNIPAM block decorated with [similar]2 mol% of azobenzene groups (P(NIPAM-co-MAzo)). In the mixed solvent of water and dioxane, the cloud point temperature (CPT) for the phase transition of the PNIPAM block displays a large shift >10 [degree]C induced by the photoisomerization of azobenzene under UV or visible light. The CPT shift of PNIPAM is highly dependent on the solvent composition and the large shift only occurs at high dioxane concentration (>30%). The mechanism of the photo-induced large CPT shift by the isomerization of azobenzene was investigated by means of 1H NMR spin relaxation studies. With the addition of dioxane, the exchange of hydrogen bonding from PNIPAM-water