diff --git a/clang/test/Headers/mm3dnow.c b/clang/test/Headers/mm3dnow.c
index a9b6dd88f8034..e45acb12ddbde 100644
--- a/clang/test/Headers/mm3dnow.c
+++ b/clang/test/Headers/mm3dnow.c
@@ -2,6 +2,9 @@
 // RUN: %clang_cc1 -fsyntax-only -D_CLANG_DISABLE_CRT_DEPRECATION_WARNINGS -ffreestanding %s -verify
 // RUN: %clang_cc1 -fsyntax-only -ffreestanding -x c++ %s -verify
 
+// XFAIL: target=arm64ec-pc-windows-msvc
+// These intrinsics are not yet implemented for Arm64EC.
+
 #if defined(i386) || defined(__x86_64__)
 #ifndef _CLANG_DISABLE_CRT_DEPRECATION_WARNINGS
 // expected-warning@mm3dnow.h:*{{The <mm3dnow.h> header is deprecated}}
diff --git a/clang/test/Headers/pmmintrin.c b/clang/test/Headers/pmmintrin.c
index 5b7a3a4ef6b9b..776ef75d70c54 100644
--- a/clang/test/Headers/pmmintrin.c
+++ b/clang/test/Headers/pmmintrin.c
@@ -2,6 +2,9 @@
 // RUN: %clang_cc1 -fsyntax-only -ffreestanding -x c++ %s -verify
 // expected-no-diagnostics
 
+// XFAIL: target=arm64ec-pc-windows-msvc
+// These intrinsics are not yet implemented for Arm64EC.
+
 #if defined(i386) || defined(__x86_64__)
 #include <pmmintrin.h>
 
diff --git a/clang/test/Headers/x86-intrinsics-headers.c b/clang/test/Headers/x86-intrinsics-headers.c
index 59ca354e1160b..dc06cbde0f587 100644
--- a/clang/test/Headers/x86-intrinsics-headers.c
+++ b/clang/test/Headers/x86-intrinsics-headers.c
@@ -2,6 +2,9 @@
 // RUN: %clang_cc1 -fsyntax-only -ffreestanding -flax-vector-conversions=none %s
 // RUN: %clang_cc1 -fsyntax-only -ffreestanding -x c++ %s
 
+// XFAIL: target=arm64ec-pc-windows-msvc
+// These intrinsics are not yet implemented for Arm64EC.
+
 #if defined(i386) || defined(__x86_64__)
 
 #ifdef __SSE4_2__
diff --git a/clang/test/Headers/x86intrin.c b/clang/test/Headers/x86intrin.c
index 53e369559f408..c01af1a43d1fa 100644
--- a/clang/test/Headers/x86intrin.c
+++ b/clang/test/Headers/x86intrin.c
@@ -3,6 +3,9 @@
 // RUN: %clang_cc1 -fsyntax-only -ffreestanding -x c++ %s -verify
 // expected-no-diagnostics
 
+// XFAIL: target=arm64ec-pc-windows-msvc
+// These intrinsics are not yet implemented for Arm64EC.
+
 #if defined(i386) || defined(__x86_64__)
 
 // Include the metaheader that includes all x86 intrinsic headers.
diff --git a/clang/test/Headers/x86intrin.cpp b/clang/test/Headers/x86intrin.cpp
index 11d442db3d2c4..6c9baa6fff635 100644
--- a/clang/test/Headers/x86intrin.cpp
+++ b/clang/test/Headers/x86intrin.cpp
@@ -1,6 +1,9 @@
 // RUN: %clang_cc1 -fsyntax-only -ffreestanding %s -verify
 // expected-no-diagnostics
 
+// XFAIL: target=arm64ec-pc-windows-msvc
+// These intrinsics are not yet implemented for Arm64EC.
+
 #if defined(i386) || defined(__x86_64__)
 
 // Include the metaheader that includes all x86 intrinsic headers.