<p>The aim of this study was to fabricate the nanocapsules and nanofibers with latent heat energy storageproperties. Therefore, phase change materials based on fatty alcohols were used as latent heat energystorage materials. N-Dodecanol and 1-tetradecanol fatty alcohols were nanoencapsulated bypoly(methyl methacrylate-co-methacrylic acid) (p(MM-co-MA)) wall using emulsion polymerizationmethod. Prepared nanocapsules were incorporated in polyacrylonitrile nanofibers using the co-axialelectrospinning method. In this study, a two-stage (TS) emulsion polymerization process was definedand compared to the known emulsion polymerization method defined as one-stage (OS).Nanocapsules were characterized by Fourier-transform infrared (FT-IR) spectroscopy, transmissionelectron microscopy (TEM), differential scanning calorimeter (DSC), and thermogravimetric analyzer(TGA). According to the results, typical core-shell structured, spherical-shaped, uniform nano-sizedparticles having high thermal stability and energy storage capacity were fabricated successfully.Enthalpy values of the nanocapsules prepared by the TS process were higher and reached up to 171J/g. It was concluded that the thermal degradation stability of the nanocapsules could be improvedusing the TS emulsion polymerization method. Moreover, the nanocapsules were incorporated inpolyacrylonitrile nanofibers using the co-axial electrospinning method, and composite nanofibershaving 19 J/g energy storage capacities were produced. Although the surfaces of the prepared coresheath structured nanofibers were rough and coarse, their diameter distribution was unimodal.<br></p>