diff --git a/src/jitlayers.cpp b/src/jitlayers.cpp
index 90091cc1f38db..a60396cfca5df 100644
--- a/src/jitlayers.cpp
+++ b/src/jitlayers.cpp
@@ -1897,7 +1897,17 @@ void optimizeDLSyms(Module &M) JL_NOTSAFEPOINT_LEAVE JL_NOTSAFEPOINT_ENTER {
 void fixupTM(TargetMachine &TM) {
     auto TheTriple = TM.getTargetTriple();
     if (jl_options.opt_level < 2) {
-        if (!TheTriple.isARM() && !TheTriple.isPPC64() && !TheTriple.isAArch64())
+        // Try GlobalISel on AArch64 - it's the default in LLVM at -O0 and
+        // is apparently generally faster than SelectionDAG while producing good code.
+        // Use fallback mode so unsupported patterns fall back to SelectionDAG.
+        // Note: Requires RemoveJuliaAddrspacesPass to run before codegen
+        // because GlobalISel doesn't handle Julia's custom address spaces.
+        if (TheTriple.isAArch64()) {
+            TM.setGlobalISel(true);
+            TM.setGlobalISelAbort(GlobalISelAbortMode::Disable);
+            TM.setFastISel(false);
+        }
+        else if (!TheTriple.isARM() && !TheTriple.isPPC64())
             TM.setFastISel(true);
         else    // FastISel seems to be buggy Ref #13321
             TM.setFastISel(false);
diff --git a/test/atomics.jl b/test/atomics.jl
index 369a63f7d5fbf..b212bd118becb 100644
--- a/test/atomics.jl
+++ b/test/atomics.jl
@@ -1115,3 +1115,15 @@ function add_one57190!()
 end
 
 @test add_one57190!() == 1
+
+# Test atomic Float16 operations at all optimization levels (GlobalISel miscompile on AArch64)
+# See https://github.com/JuliaLang/julia/pull/54140#issuecomment-2855794363
+for opt in 0:3
+    @test success(run(```$(Base.julia_cmd()) --startup-file=no -O$opt -e '
+        a = Threads.Atomic{Float16}(Float16(0))
+        a[] = Float16(1.5)
+        @assert a[] === Float16(1.5) "atomic Float16 store failed: got \$(a[]) expected 1.5 (opt level = -O$(Base.JLOptions().opt_level))"
+        a[] = Float16(3.25)
+        @assert a[] === Float16(3.25) "atomic Float16 store failed: got \$(a[]) expected 3.25 (opt level = -O$(Base.JLOptions().opt_level))"
+    '```))
+end