<p>This study investigates the structural, optical and dielectric behaviour of Nd³⁺-doped Sr₂ZnTeO₆ double-perovskite ceramics, Sr₂Zn_1-<i>x</i>Nd_<i>x</i>TeO₆ (0.0 ≤ <i>x</i> ≤ 0.2), synthesised by a conventional solid-state route. Rietveld-refined X-ray diffraction confirms the retention of a single-phase monoclinic double-perovskite structure for all compositions, with a systematic increase in unit-cell volume, microstrain, and dislocation density as Zn²⁺ is progressively replaced by larger Nd³⁺ ions, evidencing lattice distortion and grain refinement. FTIR and Raman spectra corroborate the modification of BO₆ vibrational modes with doping, UV–Vis diffuse reflectance spectroscopy shows that Nd³⁺ substitution induces only a slight narrowing of the wide optical band gap while preserving strong UV transparency, consistent with the introduction of localised 4f states and subtle band-edge renormalisation. FESEM and EDX analyses revealed homogeneous distribution of Nd ions and grain evolution with doping. Complex Impedance and dielectric measurements over 10&#xa0;Hz–10&#xa0;MHz reveal that all compositions exhibit moderate, frequency-stable dielectric permittivity in the kHz–MHz range, accompanied by relatively low dielectric loss and high bulk resistance. Depressed semicircles in Nyquist plots and broad features in the electric modulus spectra indicate non-Debye relaxation arising from grain and grain-boundary contributions, while the AC conductivity follows Jonscher’s power law, pointing to defect-assisted hopping conduction. Nd³⁺ doping enhances low-frequency permittivity and interfacial polarisation through strain and vacancy-induced defect centres, without severely increasing loss at higher frequencies. These results establish a clear correlation between aliovalent Nd³⁺ substitution, lattice distortion, defect chemistry, and dielectric response, positioning Nd-doped Sr₂ZnTeO₆ as a promising wide-ranged band-gap ceramic dielectric for potential use in UV/near-UV optoelectronic and energy-related applications.</p>