Ag-24.5 at%Ge/Ni (Co) interfacial reactions were investigated at 400 °C and 750 °C. CoGe and β-Co5Ge3 phases are formed in the Ag-24.5 at%Ge/Co) couples. Only the ε-Ni5Ge3 phase is formed in the Ag-24.5 at%Ge/Ni couples. Ag-24.5 at%Ge/Co has slower reaction rates than those in Ag-24.5 at%Ge/Ni. Co is a more suitable barrier layer than Ni if Ag-Ge eutectic is used as braze.