diff --git a/clang/lib/Driver/ToolChains/Darwin.cpp b/clang/lib/Driver/ToolChains/Darwin.cpp
--- a/clang/lib/Driver/ToolChains/Darwin.cpp
+++ b/clang/lib/Driver/ToolChains/Darwin.cpp
@@ -3279,7 +3279,8 @@
 
   if ((IsX86_64 || IsAArch64) && isTargetMacOSBased()) {
     Res |= SanitizerKind::Thread;
-  } else if (isTargetIOSSimulator() || isTargetTvOSSimulator()) {
+  } else if (isTargetIOSSimulator() || isTargetTvOSSimulator() ||
+             isTargetWatchOSSimulator()) {
     if (IsX86_64)
       Res |= SanitizerKind::Thread;
   }
diff --git a/clang/test/Driver/fsanitize.c b/clang/test/Driver/fsanitize.c
--- a/clang/test/Driver/fsanitize.c
+++ b/clang/test/Driver/fsanitize.c
@@ -463,6 +463,9 @@
 // RUN: %clang --target=x86_64-apple-ios-simulator -fsanitize=thread %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-TSAN-X86-64-IOSSIMULATOR
 // CHECK-TSAN-X86-64-IOSSIMULATOR-NOT: unsupported option
 
+// RUN: %clang --target=x86_64-apple-watchos-simulator -fsanitize=thread %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-TSAN-X86-64-WATCHOSSIMULATOR
+// CHECK-TSAN-X86-64-WATCHOSSIMULATOR-NOT: unsupported option
+
 // RUN: %clang --target=x86_64-apple-tvos-simulator -fsanitize=thread %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-TSAN-X86-64-TVOSSIMULATOR
 // CHECK-TSAN-X86-64-TVOSSIMULATOR-NOT: unsupported option