Thermal gas-phase unimolecular decomposition of the atmospherically important greenhouse molecule, SF5CF3, is studied theoretically. The density functional theory method M06-2X is used to explore the potential energy surface of the unimolecular reaction of SF5CF3. Molecular energies are refined by single-point energy calculations by the combination CBS-Q electronic structure method. Next, statistical rate theories are employed to compute the thermal rate coefficients for important product channels as a function of temperature and pressure. Variable reaction coordinate-transition state theory (VRC-TST) is employed to calculate the rate constants for the reaction channels involving bond dissociations. The pressure dependence of the thermal rate coefficients is accounted for by a master equation formalism. The major reaction channel for the dissociation of SF5CF3 is found to be CS bond cleavage producing SF5 and CF3 radicals with the Arrhenius equation as k1=2.0ÿ1016s1 exp (265.4kJmol1/RT). The present theoretical work may inspire experimental works regarding the unimolecular decomposition of SF5CF3.