The thermodynamic stability of nickel tellurate was established by studying the heterogeneous equilibrium Ni₃TeO₆(s)= 3NiO(s)+TeO₂(g)+1/2 O₂(g). Using the transpiration technique, the equilibrium constant of the reaction was obtained from the vapor pressure measurement of TeO₂(g) over the biphasic mixture of Ni₃TeO₆(s) and NiO(s) under 1 bar oxygen pressure. From the equilibrium data the second-law value of Δ_f H°(Ni₃TeO₆(s), 298.15 K) was found to be -1216(±14) kJ mol^-1. The energy change of the heterogeneous reaction derived from the equilibrium constant was used to calculate the Gibbs energy of formation of Ni₃TeO₆ as could be expressed by Δ_fG°(Ni₃TeO₆(s))(± 13 kJmol ^-1=- 1307+0.64 T, (1122 K≤T≤ 1202 K). The above Gibbs energy data were found to be consistent with the available thermodynamic information of the Ni–Te–O ternary system.