This　study　explored　the　effects　of　T5　and　T6　heat　treatments　on　the　microstructure　and　tensile　properties　of　a　laser　powder　bed　fusion　(LPBF)-fabricated　Al-Mn-Mg-Sc-Zr　alloy.　The　as-built　condition　exhibited　a　bi-modal　grain　structure　of　equiaxed　and　columnar　grains.　Specimens　after　T5　heat　treatment　also　had　a　bi-modal　microstructure　with　slight　grain　growth　and　the　precipitation　of　secondary　Al3Sc,　which　enhanced　the　yield　strength　via　precipitation　hardening　but　reduced　ductility.　In　contrast,　T6　treatment　triggered　recrystallization,　and　the　microstructure　was　only　coarse　equiaxed　alpha-Al　grains.　This　microstructure　change　was　accompanied　by　coarsened　primary　Al3X　and　Al6(Mn,　Fe)　precipitates,　partial　Mg2Si　dissolution,　and　significant　secondary　Al3Sc　particle　growth.　Consequently,　T6-treated　specimens　showed　lower　strength　than　their　T5　counterparts　and　the　poorest　ductility　due　to　brittle　fracture　induced　by　the　stress　concentration　effect　of　coarse　precipitates　at　grain　boundaries.