Glass–ceramics of 80GeS2·20In2S3 were fabricated by heat-treating the base glass at 402°C (Tg + 30°C) for different durations. The glass–ceramics exhibited some improved mechanical properties such as hardness and resistance to crack propagation, and meanwhile remained an excellent infrared (IR) transmission. The XRD and Raman results showed that only In2S3 crystals were precipitated inside glassy matrix. The evolution of two crystallization peaks (CPs) in differential scanning calorimeter (DSC) curves were studied with samples heat-treated at 402°C for different durations. It was found that the precipitation of In2S3 crystal phase is responsible for the low-temperature (first) CP, whereas the high-temperature (second) CP shifts to a higher temperature with the elongation of the heat-treatment duration. The crystallization of the higher temperature phase was inhibited with the precipitation of In2S3. Furthermore, crystallization mechanism was investigated using the nonisothermal method. The computed results showed that strictly more energy (higher activation energy, Ec) is essential for the precipitation of the higher temperature phase, which is in accordance with the DSC study of crystallized samples. More noticeable, the crystallization rate constant (K) value of 6.639 × 10−8 s−1 for the second CP is ~ 5 orders of magnitude smaller than that of the In2S3 phase, and this significant difference makes the crystallization of higher temperature crystal phase very hard. Consequently, controllable crystallization of 80GeS2·20In2S3 chalcogenide glass–ceramics with sole In2S3 crystallites can be achieved easily.