Nb/CeO₂ catalysts with different morphologies for the selective catalytic reduction of NO_x with NH₃ (NH₃-SCR) were fully studied. A Nb/CeO₂ nanoparticle catalyst presented better NH₃-SCR performance than Nb/CeO₂ nanorods, and a Nb/CeO₂ nanocube catalyst presented the lowest NO_x conversion. Transmission electron microscopy, N₂ physisorption, X-ray powder diffraction, X-ray photoelectron spectroscopy, temperature-programmed reduction with H₂ (H₂-TPR), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) were used to characterize the samples. The obtained results reveal that larger specific surface area, more abundant surface oxygen species and acid sites, lower crystallinity, and stronger redox capability of the Nb/CeO2 nanoparticle catalyst all contributed to its better NH₃-SCR performance.