The synthesis of highly ordered carbonaceous materials, including carbon nanofibers, has been the subject of a disparate and burgeoning literature over the past decade. The growth of carbon nanofibers by an atypical catalytic route, the decomposition of chlorobenzene over (10%w/w) Ni/SiO2, is considered in this paper. The reaction of chlorobenzene with hydrogen in the temperature range 550–700 °C also generated benzene via hydrodechlorination and a volatile component that results from catalytic hydrocracking/hydrogenolysis, The characteristics of the carbonaceous product are illustrated through a combination of high resolution transmission electron microscopy (HRTEM) and temperature programmed oxidation (TPO). The response of carbon yield and structural order to varying reaction time (up to 4 h on-stream) and temperature are presented and discussed. Under identical reaction conditions, the chlorobenzene feed delivered appreciably higher carbon yields than that recorded for the decomposition of benzene while the carbon growth in the former case was significantly more ordered. These findings are discussed in terms of Cl/catalyst interaction(s) and metal site restructuring.