Copper indium diselenide (CuInSe2) compound was synthesized by reacting its elemental components, i.e., copper, indium, and selenium, in stoichiometric proportions (i.e., 1:1:2 with 5% excess selenium) in an evacuated quartz ampoule. Structural and compositional characterization of synthesized pulverized material confirms the polycrystalline nature of tetragonal phase and stoichiometry. CuInSe2 thin films were deposited on soda lime glass substrates kept at different temperatures (300-573 K) using flash evaporation technique. The effect of substrate temperature on structural, morphological, optical, and electrical properties of CuInSe2 thin films were investigated using X-ray diffraction analysis (XRD), atomic force microscopy (AFM), optical measurements (transmission and reflection), and Hall effect characterization techniques. XRD analysis revealed that CuInSe2 thin films deposited above 473 K exhibit (112) preferred orientation of grains. Transmission and reflectance measurements analysis suggests that CuInSe2 thin films deposited at different substrate temperatures have high absorption coefficient (10(4) cm(-1)) and optical energy band gap in the range 0.93-1.02 eV. Results of electrical characterization showed that CuInSe2 thin films deposited at different substrate temperatures have p-type conductivity and hole mobility value in the range 19-136 cm(2)/Vs. Variation of energy band gap and resistivity of CuInSe2 thin films deposited at 523 K with thickness was also studied. The temperature dependence of electrical conductivity measurements showed that CuInSe2 film deposited at 523 K has an activation energy of 30 meV.