Abstract: Molybdenum and its alloys were widely used in extreme environments due to their excellent high-temperature properties, yet the reliable joining with dissimilar materials remains challenging. The recent research advances in the heterogeneous welding of Mo with refractory/active/ferrous metals and non-metals, were reviewed(e.g., graphite, ceramics). Brittle intermetallic compounds(e.g., Fe₂Mo, Mo₂C) were prone to form during welding with metals,and high residual stresses were generated from thermophysical mismatch in metal joints; and intrinsically brittle TiC/TiN reaction layers the fracture origin at the graphite/ceramic interface-in non-metal joints. Although interlayer design and process optimization partially mitigated these problems, bottlenecks persisted, such as unclear high-temperature long-term reliability, insufficient understanding of interfacial reactions, high cost, and narrow processing windows. Based on a critical analysis of system- specific challenges, future directions were proposed to support engineering applications of Mo-based dissimilar structures.