diff --git a/.github/workflows/windows-alt.yml b/.github/workflows/windows-alt.yml
index 5d808ad19..e25ef8350 100644
--- a/.github/workflows/windows-alt.yml
+++ b/.github/workflows/windows-alt.yml
@@ -63,12 +63,64 @@ jobs:
           options: |
             CMAKE_SYSTEM_NAME=Windows \
             CMAKE_SYSTEM_PROCESSOR=x86_64 \
-            CMAKE_BUILD_TOOL=ninja.exe \
+            CMAKE_MAKE_PROGRAM=ninja.exe \
             CMAKE_BUILD_TYPE=Release \
       - name: Build Project
         run: cmake --build ./build --target all
       - name: Run tests
         run: cmake --build ./build --target run_tests
+  clang-cl:
+    if: github.repository_owner == 'aws'
+    strategy:
+      fail-fast: false
+      matrix:
+        target:
+          - x64
+          - x64_arm64
+    runs-on: windows-latest
+    steps:
+      - if: ${{ matrix.target  == 'x64' }}
+        name: Install NASM
+        uses: ilammy/[email protected]
+      - name: Remove wrong clang-cl.exe
+        run:  rm "C:/Program Files/LLVM/bin/clang-cl.exe"
+      - name: Checkout
+        uses: actions/checkout@v4
+      - uses: TheMrMilchmann/setup-msvc-dev@v3
+        with:
+          arch: ${{ matrix.target }}
+      - if: ${{ matrix.target  == 'x64' }}
+        name: Setup CMake
+        uses: threeal/[email protected]
+        with:
+          generator: Ninja
+          c-compiler: clang-cl
+          cxx-compiler: clang-cl
+          options: |
+            CMAKE_CROSSCOMPILING=${{ ((matrix.target  == 'x64') && '0') || '1' }} \
+            CMAKE_SYSTEM_NAME=Windows \
+            CMAKE_SYSTEM_PROCESSOR=x86_64 \
+            CMAKE_BUILD_TYPE=Release \
+      - if: ${{ matrix.target  == 'x64_arm64' }}
+        name: Setup CMake
+        uses: threeal/[email protected]
+        with:
+          generator: Ninja
+          c-compiler: clang-cl
+          cxx-compiler: clang-cl
+          options: |
+            CMAKE_CROSSCOMPILING=1 \
+            CMAKE_SYSTEM_NAME=Windows \
+            CMAKE_SYSTEM_PROCESSOR=ARM64 \
+            CMAKE_C_COMPILER_TARGET=arm64-pc-windows-msvc \
+            CMAKE_ASM_COMPILER_TARGET=arm64-pc-windows-msvc \
+            CMAKE_CXX_COMPILER_TARGET=arm64-pc-windows-msvc \
+            CMAKE_BUILD_TYPE=Release \
+      - name: Build Project
+        run: cmake --build ./build --target all
+      - if: ${{ matrix.target  == 'x64' }}
+        name: Run tests
+        run: cmake --build ./build --target run_tests
   cross-mingw:
     if: github.repository_owner == 'aws'
     runs-on: ubuntu-22.04
@@ -95,4 +147,3 @@ jobs:
       - name: x86_64-w64-mingw32 Build/Test
         run:
           ./tests/ci/run_cross_mingw_tests.sh x86_64 w64-mingw32 "-DCMAKE_BUILD_TYPE=Release"
-
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 3089697c7..8dace468f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -347,7 +347,15 @@ if(GCC OR CLANG)
   # TODO(CryptoAlg-759): enable '-Wpedantic' if awslc has to follow c99 spec.
   if(CLANG OR (GCC AND CMAKE_C_COMPILER_VERSION VERSION_GREATER "4.1.3"))
     # GCC 4.1.3 and below do not support all of these flags or they raise false positives.
-    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fvisibility=hidden -Wall -Wextra -Wno-unused-parameter -Werror")
+    if (MSVC)
+      # clang-cl sets different default warnings than clang. It also treats -Wall
+      # as -Weverything, to match MSVC. Instead -W3 is the alias for -Wall.
+      # See http://llvm.org/viewvc/llvm-project?view=revision&revision=319116
+      set(C_CXX_FLAGS "${C_CXX_FLAGS} -W3 -Wno-unused-parameter -fmsc-version=1900 -Werror")
+      set(C_CXX_FLAGS "${C_CXX_FLAGS} -Wno-deprecated-declarations")
+    else()
+      set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fvisibility=hidden -Wall -Wextra -Wno-unused-parameter -Werror")
+    endif()
     set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wunused -Wcomment -Wchar-subscripts -Wuninitialized -Wshadow")
     set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wwrite-strings -Wformat-security -Wunused-result")
     set(C_CXX_FLAGS "${C_CXX_FLAGS} -Wvla -Wtype-limits")
@@ -359,12 +367,7 @@ if(GCC OR CLANG)
   endif()

   set(C_CXX_FLAGS "${C_CXX_FLAGS} -Werror -Wformat=2 -Wsign-compare -Wmissing-field-initializers -Wwrite-strings")
-  if(MSVC)
-    # clang-cl sets different default warnings than clang. It also treats -Wall
-    # as -Weverything, to match MSVC. Instead -W3 is the alias for -Wall.
-    # See http://llvm.org/viewvc/llvm-project?view=revision&revision=319116
-    set(C_CXX_FLAGS "${C_CXX_FLAGS} -W3 -Wno-unused-parameter -fmsc-version=1900")
-  else()
+  if(!MSVC)
     if(EMSCRIPTEN)
       # emscripten's emcc/clang does not accept the "-ggdb" flag.
       set(C_CXX_FLAGS "${C_CXX_FLAGS} -g")