Chalcopyrite AgInS 2 :Sn thin films were prepared by spray pyrolysis technique for a constant ratio of [Ag]/[In]=1.5 and different SnCl 4 concentrations (0.05, 0.1 and 0.2ml) in the spray solution obtaining x=[SnCl 4 ]/[Ag]+[In]=0.01, 0.02, 0.04. All films were deposited at substrate temperature of 375°C. The deposited film for which x=0.02 exhibited p-type conductivity, having band-gap energies of 1.87 and 2.01eV. Photoluminescence (PL) studies reveal several PL bands located at 1.45, 1.68, 1.70, 1.80 and ∼1.88eV at 10K. Each one of these PL structures are related to different defects, the 1.45eV emission is related to indium vacancies, 1.80eV emission to interstitial silver (Ag in ) or Indium in sites of silver (Ag In ), whereas, the other emissions (1.70 and 1.88eV) are related with a donor–acceptor pair recombination and free to bound transition, respectively, due to sulphur vacancies. Sn in excess modifies the emission bands located at 1.70 and 1.88eV; we found that Sn reduces sulphur vacancies and PL spectra are dominated by acceptor impurities.