Generally, it is very difficult to obtain multistimuli-responsive hydrogel particles. Here, we introduce a novel method for the preparation of multistimuli-responsive hydrogel particles by adding water into the poly(ethylene glycol) (PEG)based hyperbranched polymers. The produced PEG-base polymers via reversible addition-fragmentation chain transfer (RAFT) polymerization become temperature-sensitive and less soluble when heated above the lower critical solution temperature (LCST) after directly adding water. Subsequently, the hydrogel particles can be formed via hyperbranch-hyperbranch coupling through disulfide exchange. The resulting hydrogel particles are temperature-, photo-, and redox-responsive.