Following recent computational discovery of the Cs₂InSbCl₆ and Cs₂InBiCl₆ compounds, density functional theory screening of their fundamental physical properties is warranted to establish their potential as optoelectronic materials. Thus, in this paper, we report the results of detailed calculations of the structural, elastic, electronic, and optical properties of the Cs₂InSbCl₆ and Cs₂InBiCl₆ crystals using the full-potential augmented plane wave plus local orbitals method with the generalized gradient approximation (GGA) and Tran–Blaha modified Becke–Johnson potential (TB-mBJ) to model the exchange–correlation interactions. Calculations were performed both with and without including spin–orbit coupling effect. Ab initio molecular dynamics calculations show the thermal stability of the title compounds at 300 K. Predicted elastic constants show that the studied materials exhibit moderate resistant to external stress, strong elastic anisotropy, ductile nature, and mechanical stability. Cs₂InSbCl₆ and Cs₂InBiCl₆ are direct bandgap (Г–Г) semiconductors. Calculated optical properties reveal that the title compounds are characterized by strong absorption in a large energy window including the high-energy part of the sun visible spectrum.