In this study, the electronic structure of AgTlTe has been studied with first-principles calculations. The density of states and band structure were studied in detail. The thermoelectric power, electrical conductivity, and electronic thermal conductivity were analyzed using the Boltzmann transport equation with the assumption of the constant relaxation time approximation and the rigid band model. By using the calculated thermoelectric properties and experimental thermal conductivity, the dimensionless figure of merit ZT was obtained. The enhancement of the thermoelectric properties of AgTlTe by adjusting carrier concentration is predicted.