This chapter focuses on the review of PBI-based composite membranes. These are composite materials with inorganic nanoparticles, such as, hygroscopic oxides, heteropolyacids and their derivates, and pyrophosphate, ionic liquids, and even carbon-based materials. Information about the membrane preparation, physicochemical characterization, proton conductivity, and fuel cell results has been provided. In most of the cases, good results have been presented in the literature, improving key properties such as the mechanical and thermal properties, and more importantly, the proton conductivity, which has impacted positively on the fuel cell performance. However, continuous investigations must be done to improve the fuel cell performance for practical applications.