Functionalization of carbon nanotubes (CNTs) was performed, during preparation of Fischer-Tropsch synthesis (FTS) cobalt nanocatalysts, to modify the surface properties of CNTs support. Common CNTs and functionalized CNTs supported cobalt nanocatalysts were prepared using microemulsion technique with cobalt loading of 15 wt%. The catalysts were characterized by Brunauer-Emmett-Teller (BET), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), temperature program reduction (TPR), H-2 chemisorption, X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) techniques. Most of the cobalt particles were homogeneously distributed inside the tubes and the rest on the outer surface of the functionalized CNTs. Functionalization of CNTs shifted the TPR reduction peaks to lower temperatures, improved the reduction degree, and increased the dispersion of cobalt particles. The proposed cobalt catalyst supported on functionalized CNTs increased the FTS rate (g HC/g cat./h), and percentage CO conversion from 0.1476, and 32.4% to 0.24, and 54%, respectively. Catalysts supported on functionalized CNTs showed better stability. (C) 2014 Elsevier B.V. All rights reserved.