Recovery of Cs-I ions was achieved using a thermoresponsive metal recovery polymer consisting of a sodium methacrylate (SMA) unit for adsorption and an N-isopropylacrylamide (NIPAAm) unit for thermoresponsiveness. The water-soluble polymer efficiently provided homogeneous adsorption at ambient temperature. After adsorption, heating of the resulting solution precipitated Cs-I-adsorbed polymers that were separable by filtration. The kinetics, pH effect, and effect of the copolymer composition ratio on Cs-I recovery were investigated. Furthermore, the washing of soil containing Cs-I ions using an aqueous solution of the polymer was examined. The washed soil was separated by filtration, and heating of the filtrate precipitated Cs-I-adsorbed polymers that could be recovered by filtration. This indicated the potential utility of thermoresponsive metal recovery polymer in the recovery of the radioactive cesium from contaminated soil.