A self-designed Ti–Zr–Cu composite foil was used as an interlayer and vacuum brazed to achieve a heterogeneous joint between the Cf/SiC composite and Nb, resulting in a well-bonded, defect-free joint with a typical interfacial microstructure of Cf/SiC/(Ti, Zr)C/(Ti, Zr)2Cu + Zr2Cu/Ti2Cu + (Ti, Nb)ss/Nb. The effects of different experimental temperatures on the microstructural evolution of the joints and the mechanical properties of the joints were investigated, and the formation mechanism of the joint interface was analyzed. The results show that the microscopic morphology and mechanical properties of the joint interface change significantly with increasing experimental temperature. As the temperature increased to 1080 °C, the shear strength increased by 150.6% compared to 1060 °C (78.09 MPa) and reached a maximum value of 195.72 MPa, but further warming to 1100 °C (144.25 MPa) resulted in a 26.3% decrease in shear strength, with the best joint achieved at 1080 °C.