Selenization is an important stage for the fabrication of thin-film solar cells. This work presents the methodology to achieve air-annealing selenization of silver antimony sulfide (AgSbS2) films deposited by chemical bath deposition (CBD) on stainless steel substrates. Selenium incorporation was carried out by heating 100 mg of selenium powder (Se, Sigma-Aldrich, 100 mesh ) at 400 ºC. The optimal distance of AgSbS2 films from the selenium source was kept at 5 cm to produce homogeneous selenization without elemental Se traces. X-ray diffraction (XRD) results showed polycrystalline silver antimony sulfide selenide (AgSb(S,Se)2) thin-films with a face-centered cubic structure (a = 5.6721 Å) and metal oxides, elemental selenium or compounds related to the stainless steel substrate were not observed. The selenization process promotes a shift on the optical band gap (Eg) from 1.71 eV to 1.50 eV associated with AgSbS2 and AgSb(S,Se)2, respectively. The air-annealing selenization demonstrates that it is not necessary the use of special atmospheres such as Nitrogen or Argon. The use of stainless steel substrates opens the opportunity to develop flexible solar cells.