Cu₂ZnSn(S,Se)₄ (CZTSSe) thin film was prepared using a simple two-step approach based on the single-source evaporation and synchronous sulfo-selenization. Composition, microstructure, morphology, and properties of the as-prepared CZTSSe thin films were investigated. XRD and Raman patterns confirmed the formation of single-phase CZTSSe solid solutions. SEM results showed that the CZTSSe thin film had a uniform morphology and large grains. EDS results revealed the composition of CZTSSe film was Cu:Zn:Sn:S:Se = 23.7:12.6:12.2:37.7:13.8 (in at%), which was in accordance with the stoichiometric Cu₂ZnSn(S,Se)₄. The optical band gap of CZTSSe thin film evaluated from its UV–Vis spectrum was 1.33 eV. The resistivity, carrier concentration, and mobility were 0.53 Ω cm, 7.9 × 10¹⁸ cm³, and 7.5 cm²/(Vs), respectively.