Effects of Ru promoted cobalt oxide nanoparticles on γ-Al 2 O 3 supported catalysts were studied for Fischer–Tropsch reaction. Homogeneously sized cobalt oxide nanoparticles with the different amount of ruthenium promoter were prepared by solvothermal method using oleic acid as capping agent. Pre-synthesized CoRuO x nanoparticles were then impregnated on γ-Al 2 O 3 support to prepare 5CoxRu/100Al 2 O 3 catalysts (5CoxRuAl), with the amount of ruthenium x=0 to 0.1. The catalysts were characterized by XRD, TEM, TPR, EDX, H 2 chemisorption and O 2 titration methods and compared with the catalyst prepared by conventional impregnation method, i.e. i-5Co0.05RuAl. Interestingly, catalysts prepared by nanoparticle impregnation method showed higher H 2 uptake and better reducibility with the concomitant increase in the activity due to the homogeneous dispersion of the Ru promoter across entire the nanoparticles as compared to the catalyst prepared by conventional impregnation method. The intimate contact between cobalt and ruthenium enhanced the site density of cobalt which was responsible for the promotional results in the case of 5CoxRuAl catalysts.