Abstract: The joining of steel and aluminum dissimilar metals is regarded as a key technology for lightweight manufacturing in new energy vehicles and rail transit. The primary challenge lies in the formation and embrittlement control of Fe–Al intermetallic compounds (IMCs) at the interface. Laser welding, characterized by concentrated heat input and highly adjustable energy, is widely adopted as an effective approach for achieving high-quality metallurgical bonding. In this paper, recent research progress in steel/aluminum laser welding is systematically reviewed, with emphasis placed on interfacial microstructure regulation and performance enhancement, reflecting a transition from empirical parameter adjustment to mechanism–process synergistic optimization. The thermodynamics of IMC phase formation and the fluid dynamic behavior of the molten pool are discussed. Furthermore, the strengthening and toughening mechanisms of advanced techniques are comparatively analyzed, including spatial beam modulation, hybrid physical field assistance, and interlayer metallurgical reconstruction (such as high-entropy alloys and nanoparticle reinforcement). Finally, existing limitations in current research are identified in the context of large-scale engineering applications, and future development directions are prospected.