We studied ZnO nanoparticle formation in a polyimide (PI) film. Polyamic acid (PAA) was spin-coated onto Zn thin films and PAA/metal films were cured at various temperatures. Transmission electron microscopy was used to characterize oxide nartoparticles in the polyimide film. Nanosize ZnO particles were formed in the polyimide film regardless of the curing temperature. The size and the density of ZnO particles depended on the curing temperature. The degree of imidization and the mobility of particles have strong effect on the formation of ZnO.