We prepared lauric acid based phase change nanocomposite embedded with chemically functionalized single-walled carbon nanohorns and measured its thermal properties. We report contrasting enhancements in thermal conductivity of such nanocomposites in the solid and liquid phase for the same loading of nanohorn inclusions. Maximum thermal conductivity enhancement in solid and liquid phase at 2 vol% is found to be similar to 37 and similar to 11%, respectively. The nanocomposites' thermal conductivity enhancement is compared with calculations of effective medium theory considering the role of interfacial thermal transport. Model calculations show that Kapitza resistance is an order of magnitude lower at the solid-solid interface compared to the solid-liquid interface. Differential scanning calorimetry study of the nanocomposites shows that the phase change temperature and enthalpy marginally increases to that of pristine material. Such a nanocomposite with enhanced thermal transport and phase change enthalpy makes it a promising candidate for thermal energy storage applications. (C) 2014 Elsevier B.V. All rights reserved.