Molecular dynamics (MD) simulations were applied to investigate proton transfer in a Nafion polymer. This study focused on Nafion 117 (Dupont) membrane at a hydration level of lambda = 4. We investigated the transport of proton at 298 K using MD simulations. The mean square displacement, radial distribution function, and movement trajectories of protons as indicated by the MD simulations were analyzed. The calculated conductivity of a single proton was consistent with the experimental value obtained for said conductivity. We further found that protons could easily be coordinated with their neighboring water molecules. In addition, multi-hydrated protons were observed from MD trajectories. This result suggested that the proton transfer that occurs in such a Nafion polymer system is due to Grotthuss and vehicle mechanisms. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.