Durability of proton exchange membrane (PEM) fuel cells is one of the most crucial issues for fuel cell commercialization. On the other hand, chemical degradation of membranes is a major factor limiting the lifetime of PEM fuel cells. In this regard, a Nafion/SnO₂ nanocomposite membrane was prepared to improve the chemical durability of the membrane in fuel cells. The water uptake, ion exchange capacity, proton conductivity, thermal and mechanical properties of membranes were investigated. Fenton's test was used as an ex situ accelerated test to evaluate the stability of membranes. It was found that the fluoride release and weight loss in the Nafion/SnO₂ nanocomposite membrane are less than those in the pure Nafion membrane, which demonstrates the improved chemical durability of the Nafion/SnO₂ nanocomposite membrane. ATR-FTIR spectra and SEM surface images of membranes support these findings. Thus the results of this study indicate that incorporation of SnO₂ nanoparticles in the Nafion membrane can improve the chemical durability, which is important for extending the lifetime of PEM fuel cells.