Investigation of third-order optical nonlinearity of complex 1, [C6H5N-R][Ni(mnt)(2)] where R= p-nitrobenzyl, mnt = maleo-nitrile-1,2-dithiolate, with 7 ns laser pulses at 532 nm shows that it exhibits negligible nonlinear absorption, but considerable nonlinear refraction. In terms of two calculated figures of merit W and B resulting from one-photon and two-photon absorptions. complex 1 may be used fur all-optical signal processing.