The action of Ni/SiO2 in the gas phase hydrodechlorination (at 573 K) of chlorobenzene, 1,3-dichlorobenzene and 1,3,5-trichlorobenzene is compared with that of a Ni/SiO2 + C composite. The latter was prepared in situ by the decomposition of chlorobenzene at 873 K to generate graphitic carbon nanofibers bearing Ni particles at the fiber tips. The Ni/SiO2 and Ni/SiO2 + C (with varying C content) catalysts have been characterized by TEM, SEM, XRD and H-2 chemisorption. While the Ni/SiO2 + C system delivered a lower initial fractional dechlorination, the composite outperformed the starting Ni/SiO2 in terms of long-term activity, an effect that is linked to the structural characteristics.