ZnAl2O4 has a spinel structure and it is widely used as ceramic, electronic and catalytic materials [1]. Zinc aluminate may be useful for photoelectronic devices because of its optical band gap of 3.8 eV [2]. ZnAl2O4 has a cubic structure with Fd3m space group symmetry [3]. There are many methods to prepare zinc aluminate spinels, such as the sol–gel method, solid-state reaction, chemical coprecipitation, combustion synthesis and hydrothermal synthesis. In the recent years, zinc aluminate spinels doped with rare earth metal ions has been investigated due to their unique luminescent properties. Beside rare earth, transition ions present interest for ZnAl2O4 doping because it can be used as a ceramic pigment. Nanocrystalline zinc aluminate doped with Cr3+ ions with a spinel structure was prepared by coprecipitation method using zinc nitrate hexahydrate, aluminium nitrate nonahydrate and chromium nitrate hexahydrate as precursors. The structure of nanocrystalline ZnAl2O4:Cr3+ spinel was investigated in terms of XRD. The XRD spectra showed that the obtained ZnAl2O4:Cr3+ nanoparticles present a single spinel phase. The topography of the surface was achieved using atomic force microscopy (AFM) measurements. Also, the optical properties of prepared sample were investigated by UV/VIS/NIR spectroscopy. This work was partially supported by the strategic grant POSDRU/88/1.5/S/50783, Project ID50783 (2009), co-financed by the European Social Fund – Investing in People, within the Sectorial Operational Programme Human Resources Development 2007-2013. [1] X. Y. Chen, C. Ma, Z. J. Zhang, B. N. Wang. Mater. Sci. Eng. B 151 (2008) 224. [2] V. Singh, R. P. S. Chakradhar, J. L. Rao, D.-K. Kim. J. of Luminescence 128 (2008) 394. [3] R. J. Hill, J.R. Craig, G.V. Gibbs. Phys. Chem. Miner. 4 (1979) 317.