A nuclear resonance photon scattering (NRPS) study of sodium cyanide (NaC15N) between 10 and 295 K is described. This temperature range covers the fully ordered phase I, the intermediate antiferroelectric phase II and the high temperature disordered cubic phase III. The scattering intensity from the 6324 keV level in 15N was measured versus temperature and a very good agreement with the calculated values has been obtained. In the calculations, one has to account for the zero-point kinetic energy of the internal vibration of the CN- ion and the lattice modes of NaCN taken from infrared (IR), Raman and vibrational density of states (VDOS). In another approach, the external modes of motion of 15N in NaCN were accounted for by using an effective Debye temperature of Θ0 = (310 ± 5) K.