Gold nanoparticles have been incorporated with high efficiency into thermoresponsive hydrogel spheres, due to the suitable relationship of the nanoparticles and pore sizes given by the gel network. The hydrogel loaded with nanoparticles remains thermoresponsive, and the loaded gold nanoparticles exhibit little aggregation as detected by plasmon resonance, and are reversibly sensitive to the refractive index and temperature of the surrounding media. The layer-by-layer growth of polyelectrolyte multilayers on the composite spheres has also been demonstrated. These thermoresponsive plasmonic microspheres are appealing for application in biological assays.