The linear and nonlinear optical properties of polyphosphazene/polynitrile alternating copolymers, -(PH2 = N - CH = N)-N, are studied, at the MP2/6-31G(d) level of approximation, by using an oligomeric approach. We report the evolution with the chain length of the geometry, charges, dipole moments, polarizabilities, and first hyperpolarizabilities of two conformers (trans-transoïd and trans-cisoïd). Comparisons with the polyphosphazene/polyacetylene and poly(thiophosphazene) structures are performed. It turns out that the polyphosphazene/polynitrile copolymers present dipole moment and polarizabilities comparable to polyphosphazene but larger (+50%) first hyperpolarizabilities. The relative response of these copolymers is comparable to the one of standard push-pull systems.