Abstract: To meet the demand for “lightweight and high-performance” structures in fields such as aerospace and automotive and break through the bottleneck of a single technology in the fabrication of steel-aluminum reticulated bimetallic composites, a cold metal transfer melting–friction stir solid-phase synergistic additive manufacturing technology was adopted to fabricate steel-aluminum reticulated bimetallic composites, and the interface microstructure and properties of the fabricated steel-aluminum reticulated bimetallic materials were investigated. The results indicate that when the tool head’s rotational speed is 600 r/min, the prepared steel-aluminum reticulated bimetallic composites exhibit a dense structure and excellent steel-aluminum interface bonding. Serving as the reinforcement of the steel-aluminum reticulated bimetallic composites, the steel mesh has an average hardness value of up to 257 HV, which significantly improves the overall hardness of the composites. The maximum tensile strength of the steel-aluminum reticulated bimetallic composites can reach 257.5 MPa, with an increase of 42.9% compared with the additive manufacturing specimens of pure aluminum alloy. The melting-solid phase synergistic additive manufacturing technology can provide theoretical and technical support for the fabrication and industrial application of steel-aluminum reticulated bimetallic composites.