Abstract: A layered heterogeneous structure of 316L stainless steel and Inconel 625 nickel-based alloy was fabricated by Cold Metal Transfer (CMT) arc additive manufacturing. The macro-forming quality, microstructural characteristics, interfacial element distribution, and mechanical properties of the deposited components were systematically investigated. The results show that the layered heterogeneous components exhibit stable formation under the CMT arc additive manufacturing process, with continuous bead overlap and good fusion both within and between layers. No obvious macroscopic defects such as pores or cracks were observed. The microstructures of the 316L and Inconel 625 deposited layers are mainly composed of cellular and equiaxed grains. A continuous metallurgical bonding is formed at the heterogeneous interface, accompanied by a distinct Fe–Ni interdiffusion zone with a width of approximately 140–160 μm, which is significantly affected by the deposition sequence. Microhardness measurements indicate that the hardness of the 316L and Inconel 625 layers is stabilized at approximately 180 HV and 220 HV, respectively, while the interface region exhibits a gradual hardness transition. Tensile test results reveal pronounced mechanical anisotropy of the layered heterogeneous structure. The specimens tested along the welding direction exhibit the highest tensile strength and elongation, reaching 609.73 MPa and 28.94%, respectively. In contrast, the mechanical properties along the build direction are weakened by the periodically distributed heterogeneous interfaces, with the tensile strength and elongation decreasing to 399.62 MPa and 11.81%, respectively.