Abstract Phase equilibria in the entire Bi–S–I ternary system were determined experimentally by means of differential thermal analysis (DTA), X-ray diffraction (XRD) techniques and EMF measurements. Several vertical sections, an isothermal section at 300K, and a liquidus surface projection of the system were constructed and two ternary compounds BiSI and Bi19S27I3 reported earlier were confirmed. The primary crystallization fields of all phases, the types and coordinates of invariant and monovariant equilibria were determined. Thermodynamic properties of the both BiSI and Bi19S27I3 ternary compounds were studied by electromotive force measurements (EMF) with the bismuth electrode. From the EMF measurements, the partial molar functions of bismuth in alloys and the standard integral thermodynamic functions of BiSI and Bi19S27I3 were calculated.