We investigated the effect on the catalytic behavior of iron and iron-copper induced by supporting the particles on "platelet" graphite nanofibers. The decomposition of CO/H-2 was selected as a probe reaction to ascertain the manner by which this unique type of support medium influences the activity and selectivity of the metal catalysts. For comparison purposes a corresponding set of experiments was carried out where the metal and bimetallic particles were dispersed on silica, a traditional support material. It was found that the overall performance of the graphite nanofiber-supported metal catalysts was superior to that of the corresponding silica-supported systems. Furthermore, it was significant to find that the structures of the solid carbon products were entirely different from those produced by the respective unsupported metal catalyst systems. These modifications in the behavior of the iron-containing particles are discussed in terms of the impact of a metal-support interaction.