Abstract Polycrystalline Na-doped p-type AgSbTe 2+ y ( y = 0, 0.02) compounds were prepared from high purity elements by a melt-quench technique followed by spark plasma sintering. The influences of Na doping and excess Te on the thermoelectric transport properties were investigated. Both Na and Te act as acceptor in AgSbTe 2 compound. Substituting Ag with Na has great influence on electron band structure and can enhance the Seebeck coefficient effectively. Adding excess Te in Na-doped samples plays a great role in optimizing the electrical and thermal conductivity. Overall, the thermoelectric performance of the Na doped nonstoichiometric AgSbTe 2 samples is greatly improved and a ZT of 1.50 is achieved at about 570 K for Ag 0.99Na 0.01SbTe 2.02 sample, representing a 30% enhancement with respect to an undoped sample at the same temperature.