In this study, polycrystalline AgGaS2 thin films were deposited by the sequential evaporation of AgGaS2 and Ag sources with thermal evaporation technique. Thermal treatment in nitrogen atmosphere for 5 min up to 700 A degrees C was applied to the deposited thin films and that resulted in the mono phase AgGaS2 thin films without the participation of any other minor phase. Structural and compositional analyses showed the structure of the films completely changes with annealing process. The measurements of transmittance and reflectance allowed us to calculate the band gap of films lying in 2.65 and 2.79 eV depending on annealing temperature. The changes in the structure with annealing process also modify the electrical properties of the films. The resistivity of the samples varied in between 2 x 10(3) and 9 x 10(6) (Omega-cm). The room temperature mobility depending on the increasing annealing temperature was in the range of 6.7-37 (cm(2) V-1 s(-1)) with the changes in carrier concentrations lying in 5.7 x 10(13)-2.5 x 10(10) cm(-3). Mobility-temperature dependence was also analyzed to determine the scattering mechanisms in the studied temperature range with annealing. The variations in the electrical parameters of the films were discussed in terms of their structural changes.