Thermoelectrics enable the direct conversion of heat into electricity and vice versa without any moving parts. This technology is particularly valuable for recovering waste heat from engines, industrial systems, or even body heat, helping to improve overall energy efficiency. CuGaTe₂ is a promising chalcopyrite compound for thermoelectric energy conversion. In this work, we investigate the effect of biaxial strain—both compressive and tensile—on its thermoelectric properties using density functional theory (DFT) implemented in Wien2K code combined with the semi-classical Boltzmann transport formalism. Biaxial deformation on the plane was simulated by modulating the c/a ratio while keeping the volume constant. We optimized structural parameters and electronic properties. After, we studied the thermoelectics parameters as a function of carrier concentration (p and n), and through these parameters we modelised a thermoelectric module and calculated its conversion efficiency as a function of the type and intensity of strain applied. Our first-principles calculations reveal a significant improvement in thermoelectric performance under moderate compressive strain of 4%, with noticeable enhancements in the figure of merit ZT (from 0.63 to 0.91), and the calculated conversion efficiency (from 4.7 % to 6.5% for a temperature difference of 75°C) . These findings highlight the potential of strain engineering as a viable strategy to optimize the electronic transport properties of CuGaTe₂ and similar chalcopyrite materials for high-efficiency thermoelectric applications.