Abstract Microencapsulation of poly(ethylene glycol) (PEG) with a silica material to form a phase-change microcapsule system is universally acknowledged as a tough job due to its hydrophilic nature. This paper reported a feasible approach for the fabrication of core-shell structured PEG/silica phase-change microcapsules (PEG@SiO2-MEPCM) through reverse emulsion-templated in-situ polycondensation. The investigation of synthetic technique indicates that the proportion of surfactant and cosurfactant plays a key role in optimizing the morphology and microstructure of the resultant microcapsules, leading to optimal heat energy-storage performance. With the determination of an optimal mass ratio of surfactant to cosurfactant as 5/6, the synthesized PEG@SiO2-MEPCM exhibits a well-defined core-shell structure with regularly spherical morphology and uniform size distribution. It also achieves a high encapsulation ratio of over 80% with a satisfactory latent heat capacity of about 130 J/g thanks to the formation of a perfect microstructure and morphology. Moreover, the PEG@SiO2-MEPCM not only exhibits a good heat energy-storage capability together with high thermal stability and good shape/form stability, but also presents reliable and durable phase-change performance in practical use. This study is notable for its synthetic technique of the core-shell structured PEG/silica phase-change microcapsules with a reliable and durable heat energy-storage capability.