The lower critical solution temperature of thermo- and photo-responsive polymers, which involve coumarin units having functions for the dual-responsivity in chloroform, was controlled by the copolymerization. The cloud points of the copolymers of 7-methacryloyloxycoumarin with methacrylic acid and methyl methacrylate as solvophobic and solvophilic comonomers, respectively, were tuned below room temperature to nearly the boiling point of chloroform. The photodimerization of the coumarin units in the copolymer resulted in a decrease of the cloud points, i.e., photoresponsivity.