<p>Natural esters exhibit excellent flame retardant and biodegradability, which help minimize power accidents and reduce environmental impact. These qualities make natural esters a promising alternative to conventional transformer insulating oils. However, the practical applications of natural esters in power equipment have been significantly restricted by their inherent limitations, including elevated viscosity, high dielectric loss, and poor oxidative stability. Nano-modification technologies present a novel methodological approach to solve these inherent constraints. A systematic analysis of the latest research developments in nano-modified natural ester transformer oils is provided in this review. The properties of various natural esters are examined, and their suitability as base fluids is evaluated, while the modification effects and mechanisms of typical nano-additives are comprehensively reviewed. The key role of nano-modification technology in improving the overall performance of natural esters is elucidated through detailed analysis of how nanoparticles influence physical properties, dielectric properties, and oxidative stability. In addition, the practical challenges facing nano-modification technology are addressed, providing valuable theoretical guidance for future developments in this field.</p>