Abstract <p>This paper presents the results of an experimental investigation of the normal total emissivity (ε_nt) of EP718 alloy in vacuum within the temperature range of 400–1400 K. The influence of three characteristic surface conditions was systematically studied: polished, as-received (mill-finished), and air-oxidized. It is shown that the surface condition is the determining factor. For the polished and as-received surfaces, good agreement with data for the foreign analogue Inconel 718 is demonstrated. For the oxidized surface, nonmonotonic dependence ε_nt(<i>T</i>) was observed, with a pronounced decrease at temperatures above 1200 K, which is attributed to the high-temperature degradation of the oxide layer in vacuum. The obtained data are of an estimative character and are of interest for the thermal modeling of gas-turbine engine components.</p>