The optical and electronic density of states (DOS) and elastic and structural properties of crystalline perovskites KSrX3 (X = Cl and F) are examined using the full potential linearized augmented plane wave (FP-LAPW) technique in the context of the Perdew, Burke and Ernzerhof’s (PBE) generalized gradient approximation (GGA), the local density approximation (LDA) and the modified Becke-Johnson exchange potential (mBJ-GGA), while the structural properties of the KSrX3 are calculated using LDA, GGA and Wu-Cohen (WC) functionals. Our findings are that the KSrF3 compound has a direct energy band gap (Eg) at (C–C) with 5.54 eV, 5.42 eV, and 10.35 eV using PBE-GGA, LDA and mBJ-GGA approximations, respectively. The KSrCl3 compound also has an indirect energy band gap (M–C) with 4.45 eV, 4.3 eV, and 7.88 eV, as discovered using PBE-GGA, LDA and mBJ-GGA approximations, respectively. The coefficient of extinction, index of refraction, dielectric function and the fountains of apex of the optical spectra are examined with regard to the computed electronic structure.