Thermosensitive hydrogels were prepared by free radical polymerization starting from a methacrylated pullulan derivative (acting as the cross-linker) and using N-isopropylacrylamide (NIPAAM) as the monomer. Several hydrogels were obtained by changing the monomer to cross-linker ratio. A significant thermosensitivity was observed only when the molar amount of NIPAAM incorporated in the network was at least eight times higher that of methacrylate groups on pullulan. The hydrogel with high amount of NIPAAM deswells more than 80% after the T-jump. The lower critical solution temperature of thermosensitive hydrogels decreases with increasing amount of NIPAAM. The mechanical properties of the hydrogels are strongly affected by the percentage of incorporated NIPAAM and by the temperature.