<p>In this study, density functional theory (DFT) was employed to investigate the structural, optoelectronic and thermodynamic properties of a novel mixed tetragonal phase structure of NaGeI₂F perovskite. According to the electronic properties, the investigated band structure reveals that the structure offers a direct bandgap of ~1.49 eV, consistent with the beginning point of absorption observed in its optical properties. This alignment between computational results and optical analysis emphasizes the reliability of the results, particularly in the absence of theoretical or experimental data for comparison with this novel compound. The optical properties were further analysed, including the real part of the dielectric constant, refractive index, reflectivity, loss functions, extinction coefficient and absorption coefficient, as functions of energy and wavelength. In addition, mechanical property assessments indicated that the bulk modulus (<i>B</i>) of NaGeI₂F increases under applied pressure, suggesting enhanced structural stability at elevated temperatures and compressive conditions. Thermodynamic evaluations, including the calculated Gibbs free energy (<i>G</i>) and entropy (<i>S</i>), provided further insights into the material’s behaviour across varying pressure and temperature regimes. This study highlights the potential of NaGeI₂F for technological applications, owing to its high stability and dependable performance under diverse environmental conditions.</p>