ABSTRACT: Pure and Er (1.30, 1.79, 2.83 and 3.53 at. %) doped ZnO nanoparticles have been synthesized by chemical co-precipitation method. The synthesized samples were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), thermo gravimetric analysis (TGA) for thermal stability, Fourier transform infrared (FTIR) spectroscopy and photoluminescence (PL) studies. The XRD measurements confirmed the hexagonal wurtzite structure of ZnO for all samples. The crystallite size of the samples decreases with increase in concentration and are compatible with the results obtained from TEM analysis. TGA analysis of the samples reveals fine thermal stability with no significant weight loss. The shifting of ZnO stretching mode from the FTIR spectra confirm the substitution of Er in ZnO host. The PL emission spectra of pure and Er doped ZnO nanoparticles exhibit similar visible emission bands with excitation wavelength 340 nm and 367 nm. However, small near band edge (UV) emissions at 387 and 398 nm are observed with excitation wavelength 340 nm. The maximum broad band green emission is detected for 1.30 at. % of Er. The auxiliary green band (GB) emissions at 523 nm, 531nm and red band emission at 650 nm confirm the presence of Er in ZnO host. Keywords: Erbium; Zinc Oxide nanoparticles; Photoluminescence; XRD; TGA