Hybrid CO2 laser/pulsed MAG welding was carried out on plates of thickness 6 mm of Domex 420 hot rolled, high strength, cold forming steel (0.067%C, 1.11%Mn) and the influence of process parameters on weld quality was investigated. The shielding gas was a mixture of Ar, He and CO2 and the filler wire used in the MAG process was Autrod 12.51 (0.08%C, 1.5%Si, 0.9%Mn). A parametric study on V butt joint preparation specimens was carried out varying wire stick out length, lateral position of arc and laser, current pulse time, pulsing frequency and voltage. Also, butt and fillet welds were produced varying MIG parameters (voltage, pulsing frequency and wire speed), angle of laser beam, lateral position of laser and arc, and gap width. The resultant welds were assessed in terms of weld shape, HAZ width, and presence of defects (undercut, blow holes, spatter). A maximum bridgeable gap width for the butt joints was determined.