High-power laser welding is expected to achieve much higher productivity than conventional joining techniques. However, the gap tolerance of laser welding is smaller than that of conventional MIG welding because of its high concentrated energy input. Aluminium alloys were welded using 2 kW and 3 kW continuous-wave Nd:YAG lasers and a MIG welder as hybrid energy sources. Overlap and fillet joints of 2 mm thick sheets were made at various welding parameters, including laser power, MIG current, voltage, and welding speed. The quality of the bead, including its appearance and macrostructure, and the tensile strength of the joints were investigated. Metal pool images during welding were taken with a high-speed video camera in order to understand the welding phenomena better. Laser-MIG hybrid welding allows a larger gap tolerance at a higher welding speed in fillet joint welding. However, there is no such benefit in overlap joint welding. MIG energy only has the effect of enlarging the weld width. The weld depth is the same as in laser welding.