Cobalt and iron are common catalysts used in the Fischer-Tropsch (FT) reaction. This paper presents the synthesis and characterization of monometallic and bimetallic cobalt and iron nanoparticles supported on carbon nanotubes (CNTs). The CNTs-supported nanocatalysts were synthesized by a wet impregnation method at various ratios of Fe:Co. The physicochemical properties of the samples were analyzed by H 2-temperature programmed reduction (TPR), CO and H 2-chemisorption analyses, transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis. The effects of incorporation of Fe into Co on the physicochemical properties of Co/CNTs in terms of degree of reduction, CO and H 2 chemisorptions and morphologies were investigated. TEM showed that metal nanoparticles were well dispersed on the external surface and inside the CNTs. For monometallic Co/CNTs and Fe/CNTs, the average metal particle size was 5±1 nm and 6±1 nm, respectively. For the bimetallic 70Co30Fe/CNTs nanocatalysts, the average particle size was found to be 4±1 nm. Metal particles attached to the outer walls were bigger than the ones inside the CNTs. H 2-TPR analysis of Co/CNTs indicated two temperature regions at 330°C (low temperature) and 491°C (high temperature). The incorporation of iron into cobalt nanocatalysts of up to 30 of the total metal loading enhanced the catalyst's H 2 and CO chemisorptions capacities and reducibility. © (2011) Trans Tech Publications, Switzerland.