Due to the importance of halide perovskite in many applications, namely optical and electronic ones, it is a challenging task to determine the precise stable studied structure for a given overall use. In view of this point, we present in this work, for the first time, theoretical calculations carried out by means of the full-potential linearized augmented plane wave (FP−LAPW) method on the CsSrI3 compound. Deep analysis of energetic and dynamical investigations shows that this compound adopts an orthorhombic Cmcm structure. Meanwhile, both bonding and mechanical properties reveal a strong ionic/anisotropic behavior of the studied materials. This trend drastically influences electronic properties, giving rise to a wide band gap energy of 4 eV. The analysis of band structure and effective mass predicts favorable properties for UV applications.