Aliquots of well-characterized Ce-brannerite were annealed at different temperatures under N2 and synthetic air atmospheres. The autoreduction of cerium at temperature was observed using thermogravimetry to monitor the mass lost as O2 was evolved. It has been shown that the brannerite structure is stable with a small fraction of Ce3+, charge-balanced by O vacancies. The range of stability was determined to be Ce4+0.975Ti2O5.95, the fully oxidized end-member, to Ce3.87+0.975Ti2O5.886, as reduced by annealing under N2 at 1075 °C. Higher temperatures under N2 led to further reduction of Ce and collapse of the brannerite structure. Ce-brannerite remained stable on heating to 1300 °C in synthetic air, with multiple steps of oxidation and reduction corresponding to changes in the average Ce oxidation state. We propose that the autoreduction of Ce at temperature is an important factor in the overall thermodynamic stability of Ce-brannerite at temperature and has a large impact on the energetics of formation of Ce-brannerite.