<p>Here, we report that a combination of vacuum melting and spark plasma sintering efficiently enhances the thermoelectric properties of the PbTe-PbSe compounds. Thermal analysis results show that all the PbTe_1−<i>x</i>Se_<i>x</i> samples have excellent thermal stability. Positron annihilation spectroscopy results indicate improvement of the crystal quality in all obtained PbTe_1−<i>x</i>Se_<i>x</i> samples. X-ray photoelectron spectroscopy studies revealed the presence of Pb²⁺, Pb⁴⁺, Te²⁻, Te⁴⁺, Se²⁻ states of Pb, Te, and Se. Meanwhile, replacing the isoelectronic cations with those of different electronegativity will lead to a variation in carrier concentration. All samples exhibit <i>p</i>-type conduction with carrier concentrations varying from 0.07 × 10¹⁹ to 7.34 × 10¹⁹&#xa0;cm⁻³, since carrier mobility changes from 4.7 to 727.7 cm² V⁻¹ s⁻¹ at room temperature. Therefore, the maximum figure of merit (<i>ZT</i>) value reaches 0.6 at 773&#xa0;K for the PbSe_0.95Te_0.05 sample benefiting from the greatly reduced thermal conductivity, which is three times more than the intrinsic PbSe. The peak <i>ZT</i> value of 0.70 at 773&#xa0;K is obtained in PbTe_0.98Se_0.02 due to the excellent power factor. Valuable insight can be obtained from a quantitative analysis of the thermoelectric transport in PbTe-PbSe compounds with the anion vacancies (Se²⁻ and Te²⁻).</p> Graphical Abstract <p></p>