<p>Pursuing a novel thermoelectric material with a high figure of merit is a compelling goal with strong commercial motivation due to several high-impact applications and market drivers. This work theoretically investigates the structural, mechanical, electronic, optical, and thermoelectric properties of Ba₂ZnTeO₆ using DFT and Boltzmann transport theory within the WIEN2k framework. The thermodynamical, mechanical, and dynamical stability is confirmed through calculated formation energy, elastic constants and phonon dispersion, respectively, and the compound is identified as ductile. The electronic structure reveals a semiconducting nature with a direct band gap (1.80&#xa0;eV), making it suitable for optoelectronic applications. Optical analyses show significant absorption in the UV region. It is noteworthy that Ba₂ZnTeO₆ exhibits a low total thermal conductivity of 2.34 Wm⁻¹&#xa0;K⁻¹ and a figure of merit (<i>ZT</i>) of 0.37 at 300&#xa0;K. Ba₂ZnTeO₆ exhibits a high Seebeck coefficient, moderate electrical conductivity, and ultra-low lattice thermal conductivity, resulting in an exceptional figure of merit (<i>ZT</i>), especially at elevated temperatures, making it promising thermoelectric material. The dimensionless figure of merit (<i>ZT</i>) of Ba₂ZnTeO₆ reaches 0.89 at 1200&#xa0;K, highlighting its considerable potential as a high-temperature thermoelectric material. Owing to its remarkable thermoelectric efficiency, intrinsic thermodynamic stability, and environmentally benign composition, Ba₂ZnTeO₆ offers a promising and sustainable alternative to conventional toxic lead-based compounds. These attributes collectively position Ba₂ZnTeO₆ as a viable candidate for next-generation thermoelectric applications in renewable and eco-friendly energy technologies.</p>