Dielectric nanocomposites play a crucial role in electrostatic energy storage for advanced electronics and highpower devices, owing to their rapid charge/discharge abilities and high-power output. As electronic systems continue to evolve toward smaller, more integrated designs, there is a growing need for advanced dielectric nanocomposites with enhanced performance. Polymer-based dielectrics are broadly used in film capacitors due to their inherent advantages, like flexibility, high breakdown strength, low dielectric loss, and affordability. However, the energy storage capacity of these polymers is constrained by their low dielectric constants. This review aims to address this limitation by investigating polymer nanocomposites enhanced with 2D nanofillers, which demonstrate superior thermal stability, energy densities, and mechanical strength compared to pure polymers and nanocomposites with 0D or 1D nanofillers. It presents an in-depth analysis of the architectural design and the latest fabrication strategies that bolster the energy storage characteristics of these materials. Furthermore, it examines the synergistic impact of structural configuration, filler dispersion, and surface functionalization in optimizing energy storage properties. Concluding with a discussion of current challenges, future directions, and potential breakthroughs, this review serves as a guide for advancing research and development in high-energy-density polymer-based dielectric nanocomposites.