The axially substituted binuclear GaCl/GaCl phthalocyanine 1 with an unsymmetrical pattern of substitution has been prepared and its nonlinear optical (NLO) properties determined. The resulting binuclear complex retains approximately the same transition energies of monomeric (RO)8PcGaCl as far as the linear optical spectrum is concerned, although 1 has a double concentration of central atoms per molecule and an enlarged conjugated ligand. The lack of significant spectral shifts in passing from mononuclear to binuclear complexes has been rationalized theoretically by means of density functional theory calculations. The purpose of the present study is to determine whether binuclearity affects the optical limiting behavior of 1 with respect to monomeric (RO)8PcGaCl in the NLO regime determined by nanosecond laser pulses.