In this paper, an investigation into the thermal conductivity of cross-linked functionalized carbon nanotubes under physical adsorption of polyethylene (PE) chains (cfCNTs/PE) is performed using molecular dynamics (MD) simulations. To have a comprehensive study, the covalently attached functional groups with two types of distribution patterns, namely mapped and wrapped configurations, are used. The cfCNT/PE shows a smaller thermal conductivity than that of pure one. Also, the results demonstrate that the thermal conductivity of cfCNTs reduces by the physisorption of PE chains. By rising the weight percentage of physisorbed PE, the thermal conductivity of cfCNT/PE reduces more. Based on the results, for the constant weight percentage of non-covalent PE chains, the thermal conductivity increases as the number of cross-linked PE chains augments.