The energy storage performance of polymer dielectrics decreases sharply owing to the inevitable conduction loss under harsh conditions, limiting their use in next-generation microelectronics and electrical power systems. However, previously reported polymer nanocomposites, which were designed to inhibit electrical conduction, are usually incorporated with a high-volume fraction of nanofillers. In this study, a novel sandwiched polymer/metal architecture with interlayered metal nanodots was prepared. Surprisingly, the dielectric properties and high-temperature energy storage performance of the polymers were significantly improved, even when the Au nanodot content was as low as 0.0035 vol%. At 150 °C, the breakdown strength and discharged energy density were 518 MV m⁻¹ and 6.25 J cm⁻³, respectively, for the optimized films, which significantly outperform the currently reported dielectric composites at high temperatures. The thermally stimulated depolarization current results and finite element simulation revealed that the interlayered discontinuous Au nanodots could introduce deep traps and form “Coulomb islands” at the interface to capture the injected charge and block carrier transport, effectively suppressing the breakdown and leakage current under high fields. This study paves the way for the development of polymer nanocomposites with superior capacitive performances at elevated temperatures.