Theoretical studies of solvent effects on the reaction of complexing ethylene and nickel dithiolene have been carried out by calculating the molecular geometry, electron distribution, and frequency of all the stagnation points existing in the reaction potential profiles by means of density functional theory methods at the B3LYP/6-31G(d) level. On the basis of frequency analysis and statistical thermodynamic theory, some thermodynamic parameters for the titled compound have been obtained for different solvents. It is shown that the bond energy of ethylene and nickel dithiolene enhances with the increase of the solvent polarity. In addition, the frontier orbital energy gaps of the two transition states will increase, while those of the product and the intermediate as well as the corresponding solvation stabilization energy will decrease. Furthermore, these results demonstrate that in polar solvents the reaction of complexing ethylene and nickel dithiolene may become easier and faster to occur and yield a more stable product. Notably, an obvious solvent effect can be observed when the value of the solvent dielectric constant lies between 1.0 and 7.58, while the solvent effect will tend to be maximal when the value of solvent dielectric constant exceeds 7.58.