Copper Indium Oxide (CuInO2) nanocrystalline powder samples with different Cu/In ratios were prepared using the conventional solid-state reaction method. The structural, morphological, and optical properties of CuInO2 samples were studied. The delafossite structure of copper indium oxide nanocrystalline samples with (0 1 2) preferential orientation is observed. With altering the composition, the particles size of the prepared powder samples changed ranging from 6 nm to 94 nm, and the energy band gaps varied from 2.20 eV to 2.37 eV. Photoluminescence intensity at 595 nm and 596 nm in the visible region enhanced with variation of Cu/In ratios.