Carbon nanofibers (CNFs) were grown via the chemical vapor deposition of C2H4 on an activated carbon (AC)-supported Ni catalyst. The texture of the CNF/AC composites can be tuned by varying the growth temperature and by treatment in reducing atmosphere prior to C2H4/H2 exposure. The Ni-catalyzed gasification of the AC support increases the microporosity of the composite and shown to be dominant throughout the composite synthesis especially during reduction, subsequent treatment in reducing atmosphere, and CNF growth at low temperatures. N2 isotherm and scanning electron microscope were used to characterize the texture and morphology of the composites. Subsequent treatment in reducing atmosphere were shown to increase the Ni catalyst activity to grow CNFs. High resolution transmission electron microscope however did not reveal any microstructural difference for Ni catalyst with and without the subsequent reduction treatment. We propose in this paper that the carbon dissolutions during treatment of the catalyst might have an implication on the CNF growth.