In this study, it was carried out the development of a poly(ethylene glycol)/cellulose phase change reactive composite as latent heat storage material for cooling application and determination of its thermal stability. Poly (ethylene glycol) (PEG) was grafted onto a cellulose backbone as solid-solid phase change material. The change in the surface morphology of the PEG1000 was studied by using a polarised optical microscopy (POM) instrument. Thermal analysis and thermal stability upon usage of the phase change composite material were performed by using a differential scanning calorimeter (DSC) instrument. The chemical analysis of the PCM composite was carried out by using a fourier transform infrared spectroscopy (FTIR) instrument. Phase change composite melted and crystallized 10 times to determine the thermal stability. The PEG1000 grafted cellulose phase change composite before 10 times thermal cycling absorbed 78.6 J/g of heat at 7.7 degrees C and released 74.4 J/g at - 5.4 degrees C whereas the PEG1000 grafted cellulose phase change composite after 10 times thermal cycling absorbed 92.7 J/g of heat at 8.3 degrees C and released 83.2 J/g at 1 degrees C during melting and freezing respectively. It was observed that Cp of the PEG1000 grafted cellulose sample was decreased compared to Cp of the pristine PEG1000. There was a considerable difference between crystal structures of pristine PEG1000 and PEG1000 grafted cellulose phase change composite. The disappearance of diisocyanate peak of TDI observed at 2228.34 cm(-1) in PEG1000 grafted cellulose sample before and after 10 times thermal cycling was accepted as the evidence of polyurethane formation. As a result, PEG1000 grafted cellulose phase change composite was found as a potential thermal energy storage material for cooling application in relevant systems.