Nanoencapsulation has emerged as an effective strategy to address challenges such as leakage during phase change while enhancing thermophysical properties of phase change materials. Dicarboxylic acids, characterized by high latent heat, low supercooling, and excellent thermal stability, are highly promising for medium-temperature thermal energy storage. However, research on the microencapsulation of these materials remains limited, with only one prior study focusing on water-soluble glutaric acid. This manuscript introduces a novel method for nanoencapsulating water-insoluble phase change materials with melting points exceeding 100 ℃, demonstrated through the nanoencapsulation of sebacic acid. The developed nanocapsules exhibited spherical morphology with particle sizes uniformly distributed between 200 and 500 nm. Key findings include a melting temperature of 130.5 ℃, a melting enthalpy of 164.4 kJ·kg-1, minimal supercooling of 2.0 ℃, an encapsulation ratio of 73.9%, and a thermal reliability of 94.5% after repeated thermal cycling. Encapsulation significantly enhanced thermal degradation resistance, improved thermal conductivity by 15.0% with just 1.0 wt% nanocapsules in thermal fluid, and reduced pumping power requirements by up to 78.0% for 10.0 wt% nanocapsule suspensions at 25 ℃ compared to the base fluid. These results highlight the great potential of sebacic acid nanocapsules for medium-temperature thermal energy storage and transfer systems.