This study explores the structural and dielectric properties of high-density polyethylene (HDPE) nanocomposites incorporating HfO₂ and Ta₂O₅ nanoparticles before and after high-voltage corona discharge (CD) treatment. The CD process, involving charge transfer in a non-uniform electric field, was employed to evaluate surface modification and die-lectric stability. Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray (EDX) analyses confirmed uniform nanoparticle dispersion within the HDPE matrix, with lim-ited agglomeration at higher filler contents. The dielectric constant (ε′), measured as a function of frequency and nanoparticle concentration, increased with filler loading due to enhanced interfacial polarization, in good agreement with the Maxwell-Garnett theo-retical model. After CD treatment, a minor reduction in permittivity was observed, likely caused by structural rearrangements and changes in charge-trapping dynamics. Overall, the results indicate that corona discharge modifies the interfacial polarization and stabi-lizes the dielectric response of HDPE/oxide nanocomposites, making them promising candidates for advanced high-voltage insulation applications.