The　friction　stir　overlap　welding　on　variable　polarity　plasma　arc　(FSOW-VPPA)　weld　was　first　proposed　for　a　complete　girth　weld　in　2219　aluminium　alloy.　The　mechanical　properties,　microstructures,　and　metallurgical　processes　of　FSOW-VPPA　in　comparison　to　single-FSW　and　VPPA　welded　joints　were　studied　in　this　paper.　The　FSOW-VPPA　welded　joint　was　characterized　by　the　modified　nugget　zone　(NZ),　thermo-mechanically　affected　weld　zone　(WZ),　heat　affected　fusion　zone　(FZ),　and　double　heat　affected　zone　(HAZ).　The　modified　NZ　was　characterized　by　＂onion-rings＂　without　the　porosity　that　appeared　in　the　VPPA　weld.　The　grains　in　the　thermo-mechanically　affected　WZ　were　finer　than　that　of　the　VPPA　weld.　In　the　second　thermal　cycle,　the　angle　of　the　direction　of　crystal　growth　from　the　horizontal　decreased　from　38　degrees　in　the　VPPA　weld　to　22　degrees.　In　contrast　with　the　single-FSW　weld,　there　was　no　serious　deformation　on　the　advancing　side　(AS).　In　general,　the　second　thermal　cycle　did　not　degrade　the　quality　of　the　weld.　The　elimination　of　pores　and　grain　refinement　improved　both　the　tensile　strength　and　elongation　of　the　FSOW-VPPA　weld　compared　to　the　VPPA　and　single-FSW　welds.　The　tensile　strength　increased　to　84.0%　compared　to　79.8%　for　the　VPPA　weld.　In　addition,　the　metallurgical　processes　were　analysed　and　compared.　(C)　2019　The　Authors.　Published　by　Elsevier　B.V.