Colloidal silica was modified to have carbon double bonds on its surface by reacting with 3-(trimetboxysilyl)propylmethacrylate. The silica-core/poly(N-isopropylacrylamide) hydrogel-shell composite particles were synthesized by emulsion polymerization in the presence of the surfacemodified silica particles. Poly(N-isopropylacrylamide) hydrogel nanocapsules were prepared by treating the core-shell composite particles with hydrofluoric acid. The temperature responsive properties of core-shell composites and hydrogel nanocapsules were measured by dynamic light scattering. The range of transition temperature was controlled by incorporating either hydrophobic or hydrophilic comonomer in the hydrogel. The hydrogel nanocapsules showed an enhanced response to the temperature variation compared with the core-shell composite particles.