Plates, 6.3 mm thick, of 2205 duplex stainless steel (DSS) were gas metal arc welded (GMAW) under the application of an axial magnetic field (0 to 15 mT) with an ER-2209 filler wire using a gas mixture of 98%Ar + 2%O₂. Microstructural characterization of the welds revealed that electromagnetic stirring (EMS) increases the content of austenite in both weld center and high temperature heat affected zone (HTHAZ). It induced a grain refining effect during freezing of the ferritic matrix which in turn enabled more sites for nucleation of austenite. This mechanism of solidification was reflected in an increase in the mechanical strength of the welds. Besides, the extent of the HTHAZ was reduced and its microhardness increased when applying the external magnetic field. It is believed that the vibration induced in this region favored the regeneration of austenite in the ferritized HTHAZ enhancing the balance of phases.