The linear and nonlinear optical properties of a series of arylvinyldiazine derivatives are investigated by means of quantum chemical first principles calculations. The UV/vis absorption spectra of the various derivatives, as well as the NLO properties previously characterized by means of EFISHG measurements, are well reproduced by the theoretical computations. The reported results provide complementary insights on the structure–properties relationships linking the nature of the chemical substituents and of the conjugated π-electron system that constitute the push–pull structure to the amplitude of the NLO responses.