Among various polymeric materials applied as polymer electrolyte membrane (PEM) for fuel cells, Nafion is known as a standard polymer so that any new material needs to be compared with it. However, low proton conductivity under anhydrous conditions at elevated temperatures due to water evaporation and consequent need for water management, and its low tolerance for fuel impurities still remain as Nafion's major shortcomings. Development of new PEM with higher conductivity at high temperatures and stability for application at anhydrous conditions is highly desired. The aim of this review is thus to specify the latest achievements made to improve the Nafion performance by means of pretreatments, incorporation of reinforcing agents, nanocomposites, blending, ionic liquids, and so on. In recent years, a significant enhancement in Nafion performance, at humidified conditions, has been reported and many efforts have been conducted to improve its performance under dried conditions. Although impressive enhancements in Nafion performance have been reported, a need for revolutionary approaches to overcome its drawbacks is undeniably needed for future works. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.