Synthesis of nanostructured powders of tetragonal Cu2ZnSnS4 (CZTS) nanocrystals was carried out based on the hot-injection process. High-quality CZTS thin films were prepared by spin coating method onto the Corning 1737 glass substrates. CZTS nanoparticles were characterized using X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM) and high resolution TEM. It is observed that a good quality CZTS film can be obtained by spin deposition at room temperature. The optical properties of the film were studied using UV–visible spectra between 300 and 1000 nm wavelength range. The direct optical band gap of the film evolved as 1.49 eV. This value is close to the ideal band gap for highest theoretical conversion efficiency of solar cell. The optical absorption coefficients of the film between 300 and 1000 nm are found to be about 2 and 7.6 × 104 cm−1, respectively. The optical dispersion parameters of the film were also determined by Wemple–DiDomenico single oscillator model.