Abstract: An embodiment method for preparing a polymer electrolyte membrane includes preparing a nanostructure including an imidazole group, mixing a benzimidazole-based polymer, the nanostructure, and a crosslinking agent including an isocyanate group to prepare a mixture, and forming the mixture in a form of a film. An embodiment fuel cell includes a polymer electrolyte membrane including a reaction product of a benzimidazole-based polymer, a nanostructure including an imidazole group, and a crosslinking agent including an isocyanate group, a cathode on a first surface of the polymer electrolyte membrane, and an anode on a second surface of the polymer electrolyte membrane opposite the first surface.