This letter reports on the investigation of temperature dependent thermal conductivity along a long-free standing graphene nanoribbon (GNR) by a one-dimensional direction-dependent phonon-boundary scattering in the frame of linearized phonon Boltzmann transport method. It is observed that GNR has highly length and width dependent thermal conductivity due to the difference between in-plane and out-of-plane phonon modes in the phonon dispersion curve. We show that phonon mediated thermal conduction increases with size, while it decreases with increasing edge roughness. These results are relevant for tailoring and engineering of the thermal conductivity of graphene nanoribbons in thermo electronic and photonic devices. (C) 2015 Elsevier B.V. All rights reserved.