<p>The dielectric and optical properties of Pr_₀.₆₇Ba_₀.₂₂Sr_₀.₁₁Mn_{₀.₉₇₅}Ni_{₀.₀₂₅}O_₃ were investigated using impedance spectroscopy over 80–400 K, revealing two dielectric transitions, Debye-type relaxation, and an electron plasma resonance at ~ 10⁵ Hz, along with very high permittivity (ε’ &gt; 10⁵) and strong thermal stability. A colossal negative dielectric constant and metal–semiconductor transitions are observed, which are well supported by Density Functional Theory (DFT) results showing a plasma-like dielectric response, half-metallic behavior, and strong spin polarization at the Fermi level. Theoretical calculations further confirm that these anomalies originate from the electronic structure and interfacial (grain/grain-boundary) polarization mechanisms, ensuring good agreement with experimental observations. Overall, this combined experimental–theoretical consistency highlights the multifunctional dielectric and electronic response of the material, making it a promising candidate for energy storage devices and advanced miniaturized electronic and capacitive applications.</p>