Abstract An environmentally friendly phase change material (PCM) was successfully prepared by encapsulating natural soy wax into polyurethane (PU) nanofibers using coaxial electrospinning technique. The morphology and the structure of the wax/PU composites were characterized. Thermal behaviors as well as mechanical properties of the composites were also investigated. The results indicated that coaxial electrospinning produced uniform fiber morphology with a core–shell structure and a homogeneous wax distribution throughout the core of the fibers. The soy wax was successfully encapsulated into PU fibers without being miscible with PU fibers. Thermal analysis results show that the enthalpy increases as the wax content increases. The fibrous structures exhibited balanced thermal storage and released properties for thermo-regulating function. The thermal properties were unaltered after 100 heating–cooling cycles, demonstrating that the composite fibers had good thermal stability and reliability. Tensile tests also indicate that the presence of wax enhanced the modulus and lowered the tensile strain.