Thin films of Cu₂Zn_1–x Mn _x SnS₄ (0 ≤ x ≤ 1) solid solutions have been obtained for the first time by the spray pyrolysis of aqueous salt solutions (copper, zinc, manganese, and tin chlorides and thiourea) at a temperature of T _S = 563 K. The films possess specific electric conductivities within σ ≈ 35–422 Ω^–1 cm^–1 and optical bandgap width E _g ^op that increases with the manganese content from 1.54 eV (x = 0) to 2.25 eV (x = 1). Electrical and optical properties of the obtained films have been studied and analyzed based on a model of polycrystalline materials with grain boundaries. The energy barriers Eb between grains have been determined. The dependence of the bandgap of Cu₂Zn_1–x Mn _x SnS₄ (0 ≤ x ≤ 1) solid solutions on the composition has been established using the results of measurements of the optical transmission and absorption coefficients.