This work presents growth and characterization of copper indium diselenide (CuInSe 2 ) nanoparticles with controllable size synthesized by a simple solvothermal process. Salts of copper(I), indium(III) and selenium powder have been used as starting precursors and ethylenediamine is used as a solvent. Nanoparticles synthesized at different temperatures have been analyzed using X-ray diffraction and transmission electron microscopy. Particle size has been calculated by dynamic light scattering. Surface morphology has also been studied by scanning electron microscopy. Optical properties of CuInSe 2 provide band gap in the range of 0.94-1.05 eV, which are nearly close to optimal intensity for solar radiation suitable for solar cell devices.