Cesium oxythiomolybdate (Cs2MoOS3) is a potential high temperature solid lubricant. It undergoes complex oxidation reactions at elevated temperatures, but continues to provide lubrication above the oxidation temperature. Therefore, in order to determine the nature of the lubricant at elevated temperature, it is necessary to understand the thermal chemistry of Cs2MoOS3 in an air environment. The thermo-oxidative stability of Cs2MoOS3 was evaluated between room temperature and 800 degreesC in air. Melting and phase transition temperatures were determined. X-ray photoelectron spectroscopy, micro-Raman scattering and x-ray diffraction were used to identify the chemical species evolved at increasing temperatures. As-received Cs2MoOS3 was not pure. It also contained cesium molybdates, molybdenum oxides, and Cs2SO4. Between 300-400 degreesC, the material began to decompose forming Cs2SO4 and MoS2. Between 400-600 degreesC, Cs2MoOS3 also formed cesium molybdates and molybdenum oxides. In addition, the Cs2SO4 began to oxidize to cesium oxides (which melted) and SOx gas. Also, MoS2 oxidized to MoO3. At approximately 700 degreesC, MoO3 began to sublime. Upon cooling from 800 degreesC, the material was primarily cesium oxides and Cs2MoO4, with small amounts of complex cesium molybdates and molybdenum oxides.