Nanocrystalline Zn1-xCoxO powders exhibiting a preferential crystal growth along the (002) plane have been synthesized in the atomic fraction, 'x', range of 0.0-0.0625 by a wet chemical method. The effect of the dopant concentration on the corresponding structural, optical and magnetic properties was also evaluated. XRD analyses evidenced the development of singlephase wurtzite with no traces of any impurity for all the dopant levels. The higher intensity of the (002) peak, when compared to the XRD peaks in bulk ZnO, indicates the preferential crystal growth along the e-axis in hexagonal wurtzite cell. The linear dependence of cell parameters a and c with 'x' suggests the actual replacement of Zn by Co ions in the host oxide lattice. Micro Raman spectroscopy measurements showed a band centered at 535cm -1, which can be assigned to a local vibrational mode related to Co species in addition to the normal modes associated with wurtzite. The relative broadening of this band at 535cm-1 was enhanced by increasing 'x'. The other characteristic bands of ZnO corresponding to A1 (E 2, E1) and E2High modes were red shifted for all Co contents. UV-vis measurements showed that the energy band gap of as-synthesized nanopowders decreased with increasing Co2+ content up to x = 0.03 and increased for higher contents. Room-temperature magnetization measurements revealed the paramagnetic behavior of the Co-doped ZnO nanopowders. © 2011 Materials Research Society.