Relaxation, adiabatic, and differential scanning calorimetry in the 2–1350 K range of temperatures are used to measure the molar heat capacity of synthesized gadolinium tantalate Gd 3 TaO 7 characterized via X-ray diffraction, scanning electron microscopy (SEM), and chemical analysis. Such thermodynamic functions of the sample as entropy, the change in enthalpy, and reduced Gibbs energy are calculated. The enthalpy of formation of Gd 3 TaO 7 from elements is determined from literature data. Gadolinium tantalate’s Gibbs energy of formation from oxides in the range of high temperatures is calculated to estimate the stability of gadolinium tantalate relative to its constituent oxides.