PbTe-based alloys are important mid-temperature thermoelectric materials. Their application temperatures are too high for Sn-based solders. Ag-Ge eutectic alloy, Ag-24.5at%Ge, and Ag-Sb eutectic alloy, Ag-41.0at%Sb, are good candidates of braze for the PbTe-based thermoelectric modules. Ni and Co are potential barrier layers. The interfacial reactions at the Ag-Ge/Ni/PbTe, Ag-Ge/Co/PbTe, Ag-Sb/Ni/PbTe and Ag-Sb/Co/PbTe are examined. Two reaction phases, CoGe and β-Co5Ge3, are formed in the Ag-Ge/Co couples reacted at both 400oC and 750oC. Only the ε-Ni5Ge3 phase is formed in the Ag-Ge/Ni couples reacted at both 400oC and 750oC. The reaction phases are different in the Ag-Sb/Ni couples reacted at 350oC and 550oC, and they are NiSb/NiSb2 and Ni3Sb/Ni5Sb2/NiSb, respectively. Only the CoSb phase is observed in the Ag-Sb/Co couples reacted at 350oC, and both CoSb and CoSb3 phases are observed in the couples reacted at 550oC. All these results reveal the reactions with Ni are of higher reaction rates.