Tungsten inert gas welding of 316 stainless steel and 99.9% pure copper using nickel as filler metal was performed. The optimized process parameters adapted for the welding process are described. The microstructural studies revealed a complex heterogeneous fusion zone microstructures characterized both by rapid cooling and poor mixing of the materials which contain main elements which are mutually insoluble. Also, the welded specimen did not expose any defects such as porosity and cracks; however, some copper diffusion through the grain boundaries of steel was observed at the steel and fusion zone interface. The microhardness shows homogeneous values at the weld root and a higher hardness with more inhomogeneity at the weld face. The tensile strength of the weld sample was measured to be 143.7 MPa. © 2020, ASM International.