Nafion - fullerene (C₆₀, C₇₀), Nafion - fellerenol (C₆₀(OH)_n (n=22-24), C₇₀(OH)₁₂) and Nafion - fullerene tris-malonate (C₆₀[C(COOH)₂]₃) composite films were prepared by casting from alcohol-water Nafion solutions doped with these additives and then drying. Proton conductivity (σ) of the films was measured at different relative humidity (RH) levels using empedance spectroscopy. It was found that Nafion - fullerene (C₆₀, C₇₀), Nafion - fullerenol (C₆₀(OH)_n (n=22-24), C₇₀(OH)₁₂) and Nafion - fullerene tris-malonate (C₆₀[C(COOH)₂]₃) composite films demonstrated increasing proton conductivity compared to pure Nafion (especially at RH < 60%). It may be possible to use them as humidity sensing membranes.