A novel magnetically responsive CuFe2O4/fatty acids/polyester composite was produced by rapid in situ synthesis approach to develop thermal energy storage as a sustainable energy source along with magnetic effectiveness. Fabrication of such composite without complex techniques or materials as well as separate application of phase change material and discrete synthesis of nanoparticles is the advantage of the present work. A series of fatty acids containing palmitic-lauric and myristic-stearic acids as phase change materials was directly incorporated into support fibers coinciding with in situ formation of copper ferrite nanoparticles as magnetic fillers. The thermal energy storage capacities of the composites were 46.3–57.2 and 45.8–56.5 J/g for fusion and freezing cycles with related operating temperatures of 37.2–53.8 and 27.5–34.5 °C. A 104.2% promotion was resulted in thermal conductivity of the samples by introducing copper ferrite nanoparticles into the composites. Besides, the samples displayed good thermal endurance and reliability after 100 thermal cycles with excellent leakage-proof properties. A very promising magnetic performance was also observed with the saturation magnetization of 2.56–5.71 emu/g for the diverse samples. The composites produced via the suggested technique have good potential for applying in various industries for the both thermal energy regulation and magnetic effectiveness.