AgIn5 (S/Se) 8 thin films were prepared by sequential chemical deposition of In2S3–Ag2Se stack films and post-deposition thermal annealing in N2 atmosphere. The formations of AgIn5S8−xSex alloy was achievable through the post-deposition treatment at 350 and 400 °C. X-ray diffraction and energy dispersive X-ray analyses were performed on the samples. The direct optical band gap value E g for the films was found to be as the order of 1.75 eV at room temperature. The photo-response measurements exhibited that AgIn5(S/Se)8 thin films are photoconductive and p-type electrical conductivity of 6.6 × 10−6 (Ω cm)−1 and thermoelectric power of +18 µV/K.