A dextran-based dual-sensitive polymer is employed to endow gold nanoparticles with stability and pH- and temperature-sensitivity. The dual-sensitive polymer is prepared by RAFT polymerization of N-isopropylacrylamide from trithiocarbonate groups linked to dextran and succinoylation of dextran after polymerization. The functionalized nanoparticles show excellent stability under various conditions and can be stored in powder-form. UV and DLS measurements confirm that the temperature-induced optical changes and aggregation behaviors of the particles are strongly dependent on pH.