The linear and nonlinear optical (L&NLO) properties, the energy difference between the highest occupied molecular orbital and the lowest unoccupied molecular orbital (HOMO-LUMO gap), the first excitation energy (E exc ), and four indices for the evaluation of the diradical character (DC) of a series of Ni dithiolene derivatives have been computed by employing density functional theory (DFT). The selected DFT functionals provide reliable results for several properties [e.g., excitation energies and (hyper)polarizabilities]. An Atoms in Molecules analysis has been performed and several related properties have been reported (e.g., the average de-[a] Institute