diff --git a/lld/COFF/SymbolTable.cpp b/lld/COFF/SymbolTable.cpp
index 435b3bf4dbab8..aeeebbb4e332a 100644
--- a/lld/COFF/SymbolTable.cpp
+++ b/lld/COFF/SymbolTable.cpp
@@ -18,6 +18,7 @@
 #include "lld/Common/Timer.h"
 #include "llvm/DebugInfo/DIContext.h"
 #include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Mangler.h"
 #include "llvm/LTO/LTO.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/Parallel.h"
@@ -631,8 +632,47 @@ Symbol *SymbolTable::addUndefined(StringRef name, InputFile *f,
   return s;
 }
 
+// On ARM64EC, a function symbol may appear in both mangled and demangled forms:
+// - ARM64EC archives contain only the mangled name, while the demangled symbol
+//   is defined by the object file as an alias.
+// - x86_64 archives contain only the demangled name (the mangled name is
+//   usually defined by an object referencing the symbol as an alias to a guess
+//   exit thunk).
+// - ARM64EC import files contain both the mangled and demangled names for
+//   thunks.
+// If more than one archive defines the same function, this could lead
+// to different libraries being used for the same function depending on how they
+// are referenced. Avoid this by checking if the paired symbol is already
+// defined before adding a symbol to the table.
+template <typename T>
+bool checkLazyECPair(SymbolTable *symtab, StringRef name, InputFile *f) {
+  if (name.starts_with("__imp_"))
+    return true;
+  std::string pairName;
+  if (std::optional<std::string> mangledName =
+          getArm64ECMangledFunctionName(name))
+    pairName = std::move(*mangledName);
+  else
+    pairName = *getArm64ECDemangledFunctionName(name);
+
+  Symbol *sym = symtab->find(pairName);
+  if (!sym)
+    return true;
+  if (sym->pendingArchiveLoad)
+    return false;
+  if (auto u = dyn_cast<Undefined>(sym))
+    return !u->weakAlias || u->isAntiDep;
+  // If the symbol is lazy, allow it only if it originates from the same
+  // archive.
+  auto lazy = dyn_cast<T>(sym);
+  return lazy && lazy->file == f;
+}
+
 void SymbolTable::addLazyArchive(ArchiveFile *f, const Archive::Symbol &sym) {
   StringRef name = sym.getName();
+  if (isArm64EC(ctx.config.machine) &&
+      !checkLazyECPair<LazyArchive>(this, name, f))
+    return;
   auto [s, wasInserted] = insert(name);
   if (wasInserted) {
     replaceSymbol<LazyArchive>(s, f, sym);
@@ -648,6 +688,8 @@ void SymbolTable::addLazyArchive(ArchiveFile *f, const Archive::Symbol &sym) {
 
 void SymbolTable::addLazyObject(InputFile *f, StringRef n) {
   assert(f->lazy);
+  if (isArm64EC(ctx.config.machine) && !checkLazyECPair<LazyObject>(this, n, f))
+    return;
   auto [s, wasInserted] = insert(n, f);
   if (wasInserted) {
     replaceSymbol<LazyObject>(s, f, n);
diff --git a/lld/test/COFF/arm64ec-lib.test b/lld/test/COFF/arm64ec-lib.test
index 617728dac0ab2..075854f62d5d4 100644
--- a/lld/test/COFF/arm64ec-lib.test
+++ b/lld/test/COFF/arm64ec-lib.test
@@ -17,6 +17,7 @@ RUN: llvm-lib -machine:arm64ec -out:sym-arm64ec.lib sym-arm64ec.obj nsym-aarch64
 RUN: llvm-lib -machine:amd64 -out:sym-x86_64.lib sym-x86_64.obj
 RUN: llvm-lib -machine:arm64ec -out:func.lib func.obj
 RUN: llvm-lib -machine:arm64ec -out:func-x86_64.lib func-x86_64.obj
+RUN: llvm-lib -machine:arm64ec -out:func-imp.lib -def:func.def
 
 Verify that a symbol can be referenced from ECSYMBOLS.
 RUN: lld-link -machine:arm64ec -dll -noentry -out:test.dll symref-arm64ec.obj sym-arm64ec.lib loadconfig-arm64ec.obj
@@ -57,6 +58,15 @@ RUN: lld-link -machine:arm64ec -dll -noentry -out:ref-thunk-2.dll func.lib ref-t
 RUN: llvm-objdump -d ref-thunk-2.dll | FileCheck -check-prefix=DISASM %s
 RUN: llvm-readobj --hex-dump=.test ref-thunk-2.dll | FileCheck -check-prefix=TESTSEC %s
 
+Pass multiple libraries containing `func` with different manglings and ensure they don't conflict with each other.
+RUN: lld-link -machine:arm64ec -dll -noentry -out:ref-thunk-3.dll func.lib loadconfig-arm64ec.obj func-x86_64.lib func-imp.lib ref-thunk.obj
+RUN: llvm-objdump -d ref-thunk-3.dll | FileCheck -check-prefix=DISASM %s
+RUN: llvm-readobj --hex-dump=.test ref-thunk-3.dll | FileCheck -check-prefix=TESTSEC %s
+
+RUN: lld-link -machine:arm64ec -dll -noentry -out:ref-thunk-4.dll ref-thunk.obj func.lib loadconfig-arm64ec.obj func-x86_64.lib func-imp.lib
+RUN: llvm-objdump -d ref-thunk-4.dll | FileCheck -check-prefix=DISASM %s
+RUN: llvm-readobj --hex-dump=.test ref-thunk-4.dll | FileCheck -check-prefix=TESTSEC %s
+
 Test linking against an x86_64 library (which uses a demangled function name).
 RUN: lld-link -machine:arm64ec -dll -noentry -out:ref-x86-1.dll ref-thunk.obj func-x86_64.lib loadconfig-arm64ec.obj
 RUN: llvm-objdump -d ref-x86-1.dll | FileCheck -check-prefix=DISASM-X86 %s
@@ -80,6 +90,11 @@ RUN: lld-link -machine:arm64ec -dll -noentry -out:start-lib-1.dll ref-thunk.obj
 RUN: llvm-objdump -d start-lib-1.dll | FileCheck -check-prefix=DISASM %s
 RUN: llvm-readobj --hex-dump=.test start-lib-1.dll | FileCheck -check-prefix=TESTSEC %s
 
+RUN: lld-link -machine:arm64ec -dll -noentry -out:start-lib-2.dll ref-thunk.obj -start-lib func.obj -end-lib loadconfig-arm64ec.obj \
+RUN:          -start-lib func-x86_64.obj -end-lib func-imp.lib
+RUN: llvm-objdump -d ref-thunk-3.dll | FileCheck -check-prefix=DISASM %s
+RUN: llvm-readobj --hex-dump=.test ref-thunk-3.dll | FileCheck -check-prefix=TESTSEC %s
+
 #--- symref.s
     .data
     .rva sym
@@ -135,3 +150,8 @@ thunksym:
     .globl func
 func:
     ret
+
+#--- func.def
+LIBRARY func.dll
+EXPORTS
+        func