Thermal characterization of glasses from the Fex[(Sb2S3)0.75(SbSI)0.25)]100−x system, for x = 0, 0.01, 0.1, 0.5, 0.8, 2, 3 and 5 at.%, in the temperature range from 300 to 770 K, was done. The DSC recordings, obtained at different heating rates, revealed three processes: glass transition, crystallization of the corresponding crystalline phases and melting of formed crystalline phases. The glass transition process was characterized with two parameters: onset glass transition temperature Tg and apparent activation energy of glass transition Eg. Also, the effect of increasing the content of iron in the glass composition on the Tg value was determined. The complex crystallization process corresponds to the crystallization of at least two crystalline phases: SbSI and Sb2S3. Due to the considerable overlapping of the exothermic peaks, crystallization kinetics was done for Sb2S3 crystalline phase in the compositions with 0.01 and 0.5 at.% of iron. Analysis was carried out by using the Johnson–Mehl–Avrami theoretical model under non-isothermal conditions. The apparent activation energy of crystal growth Ec and the value of the Avrami index n were determined. The value of Avrami index n was determined by using the Matusita–Sakka theory. It has been shown that volumetric nucleation and three-dimensional growth occur. The shape of endothermic peaks on curves, which appear behind the crystallization processes, indicated the simultaneously progress of a multiple processes. It has been found that in addition to the melting of the SbSI phase, the process of thermal decomposition of the glass also begins at given temperatures.