Fe-based composite coatings with varying B4C contents were fabricated on Cr12 mold steel by laser cladding technology. A systematic analysis was conducted to characterize the coatings’ phase composition, microstructure, microhardness, fracture toughness, and tribological properties. The results show that an appropriate addition of B4C can refine the microstructure and facilitated the precipitation of hard phases such as Fe2B, Cr7C3 and Cr2B. However, excessive B4C led to microstructural coarsening and pronounced carbide segregation. These defects ultimately resulted in the deterioration of both mechanical strength and wear resistance. When the B4C content was 8 wt.%, the cladded layer exhibited optimal comprehensive performance, with an average microhardness of 1009.8 HV0.3, approximately 1.35 times that of the substrate, and a fracture toughness of 2.05 MPa·m1/2. Friction and wear experiments demonstrated that the Fe-based composite coatings exhibited substantially reduced wear volumes compared to the substrate when subjected to varying loads, indicating their superior resistance to abrasive damage. Notably, the composite coating with 8 wt.% B4C demonstrated superior wear resistance among all tested samples. Detailed wear mechanism investigations revealed that the degradation process resulted from a combined effect of adhesive, oxidative, and abrasive interactions. The predominant wear mode exhibited dynamic transitions dependent on both the B4C concentration and the magnitude of the applied load.