Ethylene adsorption on a Ni-55 nanocluster was studied by Weal IS of the density functional theory (DFT)/B3LYP using the basis sets of 6-31G(d,p) and 86-411(41d)G in Gaussian 03. The Ni-55 nanocluster was found to have a distorted icosahedral geometry, in accordance with the experimental findings. The binding energy value for the Ni-55 nanocluster was calculated to be 3.51 eV/atom using equilibrium geometry calculations. The estimated bulk nickel binding energy was in reasonable agreement with the experimental value (4.85 versus 4.45 eV/atom). In addition, equilibrium geometry calculations were performed for ethylene adsorption on the Ni-55 nanocluster for 2 different coordination numbers of 6 and 8 with pi-adsorption modes. The related adsorption energies were computed as -0.87 and -0.68 eV, respectively.