<p>Using first-principles density functional theory calculations within the FP-LAPW framework, the structural, mechanical, electronic, and optical properties of sodium-based oxide perovskites NaZnO₃ and NaCdO₃ are systematically investigated. Structural optimization confirms that both compounds are stable in the cubic perovskite phase, with optimized lattice parameters of 3.89 Å for NaZnO₃ and 4.09 Å for NaCdO₃. The bulk modulus, shear modulus, and Poisson’s ratio further indicate brittle behavior for NaZnO₃ (B/G = 1.6) and ductile behavior for NaCdO₃ (B/G = 2.86). Electronic structure analysis reveals that both materials exhibit semiconducting behavior with indirect band gaps. Optical properties were analyzed through dielectric functions, refractive indices, and absorption spectra. In the static (zero-frequency) limit, NaZnO₃ exhibits a high refractive index of 12.8 corresponding to a dielectric constant of 150, while NaCdO₃ shows a refractive index of 9.3 with a dielectric constant of 80. These results highlight the potential of NaZnO₃ and NaCdO₃ for ultraviolet optoelectronic and photonic applications. This work provides the first comprehensive theoretical insight into the fundamental properties of NaXO₃ (X = Zn, Cd) perovskites and serves as a reference for future experimental and device-oriented studies.</p>