[en] Highly monodispersed ZnO nanoparticles with an average diameter of 8–10 nm were prepared using N-Methylaniline as an organic ligand by chemical route. Thermal stability of the size confined ZnO nanoparticles was investigated by annealing at high temperatures. Morphology of the ZnO nanoparticles has been transformed from spherical particles to nanorods at 600 °C by solid–solid interaction. Crystallinity was improved by increasing annealing temperature. As-prepared ZnO nanoparticles exhibited strong ultraviolet emission at 380 nm and annealed samples had strong green emission. X-ray photoelectron spectra results showed that ZnO had more oxygen defects at higher annealing temperatures.