diff --git a/cmake/modules/DarwinSDKs.cmake b/cmake/modules/DarwinSDKs.cmake
index 20d555b7475..53f18a1ee43 100644
--- a/cmake/modules/DarwinSDKs.cmake
+++ b/cmake/modules/DarwinSDKs.cmake
@@ -3,7 +3,7 @@ set(SUPPORTED_IOS_SIMULATOR_ARCHS "x86_64;arm64")
 set(SUPPORTED_TVOS_ARCHS "arm64")
 set(SUPPORTED_TVOS_SIMULATOR_ARCHS "x86_64;arm64")
 set(SUPPORTED_WATCHOS_ARCHS "armv7k;arm64_32")
-set(SUPPORTED_WATCHOS_SIMULATOR_ARCHS "x86_64;arm64")
+set(SUPPORTED_WATCHOS_SIMULATOR_ARCHS "i386;x86_64;arm64")
 set(SUPPORTED_OSX_ARCHS "x86_64;arm64")
 set(SUPPORTED_XROS_ARCHS "arm64;arm64e")
 set(SUPPORTED_XROS_SIMULATOR_ARCHS "arm64")
diff --git a/cmake/modules/SwiftConfigureSDK.cmake b/cmake/modules/SwiftConfigureSDK.cmake
index b1dbea4f999..45b1900a63e 100644
--- a/cmake/modules/SwiftConfigureSDK.cmake
+++ b/cmake/modules/SwiftConfigureSDK.cmake
@@ -91,6 +91,10 @@ function(remove_sdk_unsupported_archs name os sdk_path deployment_version archit
       # 32-bit watchOS is not listed explicitly in SDK settings.
       message(STATUS "Assuming ${name} SDK at ${sdk_path} supports architecture ${arch}")
       list(APPEND architectures ${arch})
+    elseif(arch STREQUAL "i386" AND os STREQUAL "watchsimulator")
+      # 32-bit watchOS simulator is not listed explicitly in SDK settings.
+      message(STATUS "Assuming ${name} SDK at ${sdk_path} supports architecture ${arch}")
+      list(APPEND architectures ${arch})
     else()
       message(STATUS "${name} SDK at ${sdk_path} does not support architecture ${arch}")
     endif()
diff --git a/utils/build-script-impl b/utils/build-script-impl
index 05d9070cda5..8ad69246b53 100755
--- a/utils/build-script-impl
+++ b/utils/build-script-impl
@@ -486,6 +486,7 @@ function verify_host_is_supported() {
       | appletvsimulator-x86_64 \
       | appletvsimulator-arm64  \
       | appletvos-arm64         \
+      | watchsimulator-i386     \
       | watchsimulator-x86_64   \
       | watchsimulator-arm64    \
       | watchos-armv7k          \
@@ -664,6 +665,13 @@ function set_build_options_for_host() {
                     SWIFT_HOST_VARIANT_SDK="TVOS"
                     cmake_osx_deployment_target=""
                     ;;
+                watchsimulator-i386)
+                    SWIFT_HOST_TRIPLE="i386-apple-watchos${DARWIN_DEPLOYMENT_VERSION_WATCHOS}-simulator"
+                    llvm_target_arch="X86"
+
+                    SWIFT_HOST_VARIANT_SDK="WATCHOS_SIMULATOR"
+                    cmake_osx_deployment_target=""
+                    ;;
                 watchsimulator-x86_64)
                     SWIFT_HOST_TRIPLE="x86_64-apple-watchos${DARWIN_DEPLOYMENT_VERSION_WATCHOS}-simulator"
                     llvm_target_arch="X86"
diff --git a/utils/build_swift/build_swift/driver_arguments.py b/utils/build_swift/build_swift/driver_arguments.py
index bc36cbf03ab..6d5759cab41 100644
--- a/utils/build_swift/build_swift/driver_arguments.py
+++ b/utils/build_swift/build_swift/driver_arguments.py
@@ -1268,6 +1268,10 @@ def create_argument_parser():
     option('--skip-test-ios-simulator',
            toggle_false('test_ios_simulator'),
            help='skip testing iOS simulator targets')
+    option('--skip-test-watchos-32bit-simulator',
+           toggle_false('test_watchos_32bit_simulator'),
+           default=False,
+           help='skip testing watchOS 32 bit simulator targets')
     option('--skip-test-ios-host',
            toggle_false('test_ios_host'),
            help='skip testing iOS device targets on the host machine (the '
diff --git a/utils/build_swift/tests/expected_options.py b/utils/build_swift/tests/expected_options.py
index 6a106f996f6..e1faa5a8769 100644
--- a/utils/build_swift/tests/expected_options.py
+++ b/utils/build_swift/tests/expected_options.py
@@ -292,6 +292,7 @@ EXPECTED_DEFAULTS = {
     'test_cygwin': False,
     'test_freebsd': False,
     'test_ios': False,
+    'test_watchos_32bit_simulator': False,
     'test_ios_host': False,
     'test_ios_simulator': False,
     'test_linux': False,
@@ -735,6 +736,8 @@ EXPECTED_OPTIONS = [
     DisableOption('--skip-test-cygwin', dest='test_cygwin'),
     DisableOption('--skip-test-freebsd', dest='test_freebsd'),
     DisableOption('--skip-test-ios', dest='test_ios'),
+    DisableOption('--skip-test-watchos-32bit-simulator',
+                  dest='test_watchos_32bit_simulator'),
     DisableOption('--skip-test-ios-host', dest='test_ios_host'),
     DisableOption('--skip-test-ios-simulator', dest='test_ios_simulator'),
     DisableOption('--skip-test-linux', dest='test_linux'),
diff --git a/utils/sil-opt-verify-all-modules.py b/utils/sil-opt-verify-all-modules.py
index b71ece1382c..34662f1ff96 100755
--- a/utils/sil-opt-verify-all-modules.py
+++ b/utils/sil-opt-verify-all-modules.py
@@ -63,6 +63,7 @@ def get_verify_resource_dir_modules_commands(
         ('iphonesimulator', 'x86_64', 'x86_64-apple-ios7.0'),
         ('macosx', 'x86_64', 'x86_64-apple-macosx10.9'),
         ('watchos', 'armv7k', 'armv7k-apple-watchos2.0'),
+        ('watchsimulator', 'i386', 'i386-apple-watchos2.0'),
     ]
 
     commands = []
diff --git a/utils/swift_build_support/swift_build_support/host_specific_configuration.py b/utils/swift_build_support/swift_build_support/host_specific_configuration.py
index 5d37027ce0c..ede1c81d74c 100644
--- a/utils/swift_build_support/swift_build_support/host_specific_configuration.py
+++ b/utils/swift_build_support/swift_build_support/host_specific_configuration.py
@@ -323,6 +323,9 @@ class HostSpecificConfiguration(object):
 
     def __platforms_archs_to_skip_test(self, args, stage_dependent_args, host_target):
         platforms_archs_to_skip_test = set()
+        if not stage_dependent_args.test_watchos_32bit_simulator:
+            platforms_archs_to_skip_test.add(
+                StdlibDeploymentTarget.AppleWatchSimulator.i386)
         if host_target == StdlibDeploymentTarget.OSX.x86_64.name:
             platforms_archs_to_skip_test.add(
                 StdlibDeploymentTarget.iOSSimulator.arm64)
@@ -338,6 +341,8 @@ class HostSpecificConfiguration(object):
                 StdlibDeploymentTarget.iOSSimulator.x86_64)
             platforms_archs_to_skip_test.add(
                 StdlibDeploymentTarget.AppleTVSimulator.x86_64)
+            platforms_archs_to_skip_test.add(
+                StdlibDeploymentTarget.AppleWatchSimulator.i386)
             platforms_archs_to_skip_test.add(
                 StdlibDeploymentTarget.AppleWatchSimulator.x86_64)
 
diff --git a/utils/swift_build_support/swift_build_support/products/cmake_product.py b/utils/swift_build_support/swift_build_support/products/cmake_product.py
index 53c0ed7ad30..6b4eaca1062 100644
--- a/utils/swift_build_support/swift_build_support/products/cmake_product.py
+++ b/utils/swift_build_support/swift_build_support/products/cmake_product.py
@@ -303,6 +303,13 @@ class CMakeProduct(product.Product):
                 swift_host_variant_sdk = 'TVOS'
                 cmake_osx_deployment_target = None
 
+            elif host_target == 'watchsimulator-i386':
+                swift_host_triple = 'i386-apple-watchos{}-simulator'.format(
+                    self.args.darwin_deployment_version_watchos)
+                llvm_target_arch = 'X86'
+                swift_host_variant_sdk = 'WATCHOS_SIMULATOR'
+                cmake_osx_deployment_target = None
+
             elif host_target == 'watchsimulator-x86_64':
                 swift_host_triple = 'x86_64-apple-watchos{}-simulator'.format(
                     self.args.darwin_deployment_version_watchos)
diff --git a/utils/swift_build_support/swift_build_support/targets.py b/utils/swift_build_support/swift_build_support/targets.py
index 508d6204eaf..53c7fc3cdbf 100644
--- a/utils/swift_build_support/swift_build_support/targets.py
+++ b/utils/swift_build_support/swift_build_support/targets.py
@@ -258,7 +258,7 @@ class StdlibDeploymentTarget(object):
                                 sdk_name="WATCHOS")
 
     AppleWatchSimulator = DarwinPlatform("watchsimulator",
-                                         archs=["x86_64", "arm64"],
+                                         archs=["i386", "x86_64", "arm64"],
                                          sdk_name="WATCHOS_SIMULATOR",
                                          is_simulator=True)
 
diff --git a/utils/swift_build_support/tests/test_host_specific_configuration.py b/utils/swift_build_support/tests/test_host_specific_configuration.py
index 6d2d98536f0..fd2c36e9e04 100644
--- a/utils/swift_build_support/tests/test_host_specific_configuration.py
+++ b/utils/swift_build_support/tests/test_host_specific_configuration.py
@@ -191,9 +191,9 @@ class ToolchainTestCase(unittest.TestCase):
             'build_watchos_device')
     test_should_skip_building_watchos_sim =\
         generate_should_skip_building_platform(
-            'watchsimulator-x86_64',
+            'watchsimulator-i386',
             'WATCHOS_SIMULATOR',
-            'swift-test-stdlib-watchsimulator-x86_64',
+            'swift-test-stdlib-watchsimulator-i386',
             'build_watchos_simulator')
 
     def generate_should_build_full_targets_when_test(test_arg_name):
@@ -233,7 +233,7 @@ class ToolchainTestCase(unittest.TestCase):
             'stress_test')
 
     def generate_should_skip_testing_platform(
-            host_target, build_arg_name, test_arg_name, extra_test_arg_name=None):
+            host_target, build_arg_name, test_arg_name):
         def test(self):
             args = self.default_args()
             setattr(args, build_arg_name, True)
@@ -245,8 +245,6 @@ class ToolchainTestCase(unittest.TestCase):
             self.assertEqual(len(before.swift_test_run_targets), 0)
 
             setattr(args, test_arg_name, True)
-            if extra_test_arg_name is not None:
-                setattr(args, extra_test_arg_name, True)
             after = HostSpecificConfiguration(host_target, args)
             self.assertIn('check-swift-{}'.format(host_target),
                           after.swift_test_run_targets)
@@ -292,10 +290,27 @@ class ToolchainTestCase(unittest.TestCase):
     # NOTE: test_watchos_host is not supported in open-source Swift
     test_should_skip_testing_watchos_sim =\
         generate_should_skip_testing_platform(
-            'watchsimulator-x86_64',
+            'watchsimulator-i386',
             'build_watchos_simulator',
-            'test_watchos_simulator',
-            'test_watchos_64bit_simulator')
+            'test_watchos_simulator')
+
+    def test_should_skip_testing_32bit_watchos(self):
+        host_target = 'watchsimulator-i386'
+        args = self.default_args()
+        args.build_watchos_simulator = True
+        args.test_watchos_simulator = True
+        args.test_watchos_32bit_simulator = False
+        args.host_target = host_target
+        args.stdlib_deployment_targets = [host_target]
+        args.build_stdlib_deployment_targets = 'all'
+
+        before = HostSpecificConfiguration(host_target, args)
+        self.assertEqual(len(before.swift_test_run_targets), 0)
+
+        args.test_watchos_32bit_simulator = True
+        after = HostSpecificConfiguration(host_target, args)
+        self.assertIn('check-swift-watchsimulator-i386',
+                      after.swift_test_run_targets)
 
     def generate_should_allow_testing_only_host(
             host_target, build_arg_name, test_arg_name, host_test_arg_name):
@@ -666,6 +681,7 @@ class ToolchainTestCase(unittest.TestCase):
             test_freebsd=False,
             test_ios_host=False,
             test_ios_simulator=False,
+            test_watchos_32bit_simulator=True,
             test_linux=False,
             test_optimize_for_size=False,
             test_optimize_none_with_implicit_dynamic=False,