An instrument capable of performing nanoindentation at temperatures up to 500 °C in inert atmospheres, including partial vacuum and gas near atmospheric pressures, is described. Technical issues associated with the technique (such as drift and noise) and the instrument (such as tip erosion and radiative heating of the transducer) are identified and addressed. Based on these considerations, preferred operation conditions are identified for testing on various materials. As a proof-of-concept demonstration, the hardness and elastic modulus of three materials are measured: fused silica (nonoxidizing), aluminum, and copper (both oxidizing). In all cases, the properties match reasonably well with published data acquired by more conventional test methods.