Thermal losses significantly affect the performance efficiency of solar devices, electronic circuits, building materials, air conditioners, refrigerators, etc. Improving thermal buffering capacity is the remedy for this problem. It is achieved by incorporating phase change materials (PCMs). PCMs can absorb, accumulate, or emit latent heat during the phase transition process at a specific temperature range, making them suitable for thermal energy storage. However, PCMs have two major drawbacks that need to be rectified before use. The first disadvantage is leakage of molten PCM, and the second is low thermal conductivity. Both problems can be resolved by preparing PCM nanocomposites. The strategies of nanocomposite preparation can be briefly classified into three methods, namely blending, encapsulation, and impregnation. The review paper discusses the effect of nanomaterial morphology on the form-stabilization of PCM. The nanomaterials can modify thermal conductivity, electrical conductivity, and mechanical properties as per application requirements. This article highlights the benefits of using thermal energy storing nanocomposites in widely used application areas such as textiles, building materials, electronics systems, and solar energy storage devices. They can also be utilized for niche applications such as shape memory polymers and infrared thermal stealth.