Extreme weather caused by global warming often leads to unfavorable temperature conditions that affect human comfort and health. To address the adverse effects, several studies have proposed the use of nano-encapsulated phase change material (PCM) in textile. Therefore, this study aims to synthesize PCM nano-capsules using the in-situ polymerization method. During the procedure, Polyethylene Glycol (PEG) 1000 and PEG 1000-paraffin composite served as the core, while urea-formaldehyde was used in the outer layer as the shell. The products obtained were then subjected to particle size analysis (PSA), scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier transform infrared (FTIR) spectroscopy, and differential scanning calorimetry (DSC) to characterize their properties. DSC results showed that PEG 1000 nano-capsules had a decomposition peak at 32.95 °C with an enthalpy of 49.37 J/g. Meanwhile, PEG 1000-Paraffin composite nano-capsules decomposition peak was at 38.77 °C, with an enthalpy of 653.22 J/g. These results showed that paraffin inclusion in the composite enhanced thermal capacity of nano-encapsulated PCM, enabling effective maintenance of temperature stability within the human comfort range of approximately 37 °C.