Abstract: Laser-CMT (cold metal transfer) hybrid welding was performed on S30408 stainless steel. The effect of laser power on weld morphology, microstructure, and mechanical properties of the hybrid weld joint was studied. An optimal laser power of 2.5 kW for single-pass hybrid welding of 5 mm thick steel plates was recognized within series laser powers. As to dual-pass welding of 10 mm thick plates, increasing the laser power from 2.5 to 4.5 kW significantly improved penetration depth and expanded the hybrid-fusion zone. Dual-pass weld joints at both laser parameters achieved more than 93% tensile strength of the base metal. However, the impact energy at -196 ℃ of the weld zone notably increased from 91.8 J (2.5 kW) to 154.5 J (4.5 kW), which was attributed to the homogeneous microstructure. Microhardness mapping revealed a hardened zone in the heat-affected zone with a maximum hardness of 241 HV₁, regardless of laser power. These results demonstrate that optimizing laser power in dual-pass hybrid welding could effectively enhance the weld joint integrity and cryogenic toughness of stainless steel.