Metal　inert　gas　(MIG)　welding　of　a　novel　Al-5.82Mg-0.61Zn-0.14Er-0.11Zr　alloy　was　performed　using　ER5E61　and　ER5B71　filler　wires.　The　effect　of　the　two　filler　wires　on　microstructures　and　mechanical　properties　of　MIG　welded　joints　was　investigated.　The　study　shows　that　fully　penetrated　joints　are　obtained　by　MIG　welding　process　filled　with　ER5E61　and　ER5B71　wires.　Compared　with　ER5B71,　the　weld　metal　(WM)　with　ER5E61　exhibits　a　coarse　structure　and　high　solid　solution　of　Mg　and　Mn　elements.　After　the　tensile　test,　the　WM　with　ER5E61　and　ER5B71　wires　is　composed　of　elongated　coarse　grains　with　a　higher　proportion　of　low　angle　grain　boundaries　(LAGBs).　In　addition,　the　lattice　rotation　occurring　within　the　grains,　indicating　that　single　grain　has　an　unevenly　plastic　deformation　after　the　tensile　test.　The　average　microhardness　of　the　WM　is　83.4　HV　and　82.9　HV　for　ER5E61　and　ER5B71　wire,　which　is　the　lowest　microhardness　in　the　MIG　welded　joint.　The　average　ultimate　tensile　strength　(UTS)　and　elongation　index　(EI)　of　the　MIG　joints　are　327.7　MPa　and　8.5%　for　ER5E61　wire,　and　314.3　MPa　and　8.2%　for　ER5B71　wire,　suggesting　the　MIG　welded　joint　with　ER5E61　wire　achieves　a　good　combination　of　strength　and　ductility.　Quantitative　assessments　of　the　effects　of　different　strengthening　mechanisms　on　the　strength　reveal　that　dislocation　strengthening　and　solid　solute　strengthening　are　the　main　factors　to　obtain　a　higher　strength　of　welded　joints　with　ER5E61.　©　2024　The　Authors