High manufacturing freedom of additive manufacturing (AM) technology, such as selective laser melting (SLM), innovates an effective way for the fabrication of multi-material components which is highly challenging or even impossible for the conventional manufacturing processes. The bonding performance between dissimilar materials in the AMed multi-material component needs further research prior to application. In this study, maraging steel (MS1) part was manufactured on top of the cast CrMn steel using SLM to obtain a multi-material component. The microstructure of CrMn steel substrate and MS1 steel, as well as the interfacial morphology of the hybrid CrMn-MS1 component, was characterized to study the metallurgical property. The microhardness and tensile property tests were conducted to investigate the mechanical behaviour of the hybrid cast/SLM multi-material component. An interface with a width of about 130 μm was formed between the two dissimilar materials. Marangoni convection caused complex phenomena at the interface, leading to the cross-regional distribution of alloy elements and a variation in the microstructure of the first several layers of SLMed MS1. Good metallurgical bonding of the dissimilar materials manufactured by SLM is achieved without pores, inclusions or cracks in the interfacial region. The microhardness value of the interface region is 309 ± 9 HV0.05 . This mitigates the difference in performance mismatch by smoothening the mechanical-property transition between CrMn steel (277 ± 11 HV0.05) and SLMed MS1 (360 ± 9 HV0.05). The hybrid CrMn-MS1 steel presents a higher ultimate tensile strength of 986 ± 30 MPa than cast CrMn steel and higher elongation of 24.5 ± 1.0% than SLMed MS1. This study proves feasibility to manufacture a reliable multi-martial component with a cast substrate and SLMed part of potentially higher complexity.