AgCu[Formula: see text]Fe[Formula: see text]S compounds were synthesized by partial Cu[Formula: see text][Formula: see text][Formula: see text]Fe replacement in the AgCuS crystal at a concentration range of 0[Formula: see text][Formula: see text][Formula: see text]x[Formula: see text][Formula: see text][Formula: see text]0.03. In the differential thermal analysis spectrum obtained at a temperature range of 300 K[Formula: see text][Formula: see text][Formula: see text]T[Formula: see text][Formula: see text][Formula: see text]1300 K, endoeffect corresponding to the structural phase transition in the AgCuS compound was observed at the temperature T[Formula: see text]=[Formula: see text]938 K. It has been determined that this result is also observed in the AgCu[Formula: see text]Fe[Formula: see text]S compound obtained by partial replacement of Cu atoms by Fe atoms. However, in the compound of AgCu[Formula: see text]Fe[Formula: see text]S this effect was observed at higher temperatures. The thermal capacities and enthalpies of phase transitions were calculated for the given compounds.