<p>In this article, we used first principles calculations to predict the structural, electronic, elastic, mechanical, and thermodynamic properties of cubic double perovskites, X₂CuIO₆ (X = Sr, Ba). These compounds were analyzed as structurally, dynamically, and thermodynamically stable based on the calculated results of the tolerance factor, formation energy, and positive phonon frequencies, respectively; additionally, the mechanical stability was confirmed by the elastic constants C₁₁, C₁₂, and C₄₄. The electronic properties demonstrated that X₂CuIO₆ perovskites are metallic since the valence and conduction bands overlap with a 0&#xa0;eV band gap at the fermi level. The mechanical properties revealed the ductile and anisotropic nature. The thermodynamic parameters, bulk modulus, volume, Debye temperature, heat capacity, and thermal expansion were calculated in a wide range of temperature and pressure using the quasi-harmonic Debye model. Up to 700&#xa0;K, the specific heat for both double perovskites was found to follow the Debye model (CV α T³); after that, it follows the Dulong-Petit law (CV ~ 3R).</p>