Carbon nanotubes (CNTs) and carbon nanofibers (CNFs) have been used for the first time to support ruthenium nanoparticles for the hydrogenation of p-chloronitrobenzene (p-CNB) to produce selectively p-chloroaniline. The preparation of well-dispersed ruthenium catalysts from the [Ru3(CO)12] precursor required activation of the purified supports by nitric acid oxidation. The supports, purified and functionalized, and the supported catalysts have been characterized by a range of techniques. The catalytic activity of these materials for the hydrogenation of p-CNB at 35 bar and 60 °C is shown to reach as high as 18 molp-CNB gRu−1 h−1, which is one order of magnitude higher than a commercial Ru/Al2O3 catalyst. Selectivities between 92 and 94 % are systematically obtained, the major byproduct being aniline.