The structure, stability, 14N NQR parameters, and hyperpolarizability of Fe(CO)4py isomers in seven different solvents were computed with the MPW1PW91 method based on the polarizable continuum model (PCM). From an energetic standpoint, the Fe(CO)4pyaxial isomer was more stable than the Fe(CO)4pyequatorial isomer. On the other hand, the relative energies decreased in more polar solvents. Molecular orbital analysis showed that the HOMO of the Fe(CO)4py isomer was distributed on the Fe(CO)4 fragment, whereas the LUMO was localized on the pyridine ligand. This study suggests that the nonlinear optical (NLO) properties depend on the solvent polarity.