A photopyroelectric measurement of the thermal parameters of glycine phosphite (GPI) single crystals across the ferroelectric phase transition temperature has been carried out. The thermal parameters-thermal diffusivity (alpha), thermal effusivity (e), thermal conductivity (K), and heat capacity (c(P))-of GPI single crystals are reported. The para-ferroelectric phase transition is reflected in these thermal parameters as anomalies at the transition point. The anisotropy in thermal wave propagation is established by measuring thermal conductivity along the a, b, and c. crystal axes. The anomalous variations in the thermal parameters across the phase transition temperature reveal an order-disorder type transition at 224 K in this crystal.