diff --git a/flang/lib/Frontend/CompilerInvocation.cpp b/flang/lib/Frontend/CompilerInvocation.cpp
--- a/flang/lib/Frontend/CompilerInvocation.cpp
+++ b/flang/lib/Frontend/CompilerInvocation.cpp
@@ -604,14 +604,24 @@
   // TODO: Currently throws a Diagnostic for anything other than -W<error>,
   // this has to change when other -W<opt>'s are supported.
   if (args.hasArg(clang::driver::options::OPT_W_Joined)) {
-    if (args.getLastArgValue(clang::driver::options::OPT_W_Joined)
-            .equals("error")) {
-      res.setWarnAsErr(true);
-    } else {
-      const unsigned diagID =
-          diags.getCustomDiagID(clang::DiagnosticsEngine::Error,
-                                "Only `-Werror` is supported currently.");
-      diags.Report(diagID);
+    const auto wArgs =
+        args.getAllArgValues(clang::driver::options::OPT_W_Joined);
+    for (const auto &wArg : wArgs) {
+      if (wArg == "error") {
+        res.setWarnAsErr(true);
+      } else if (wArg == "extra") {
+        const unsigned diagID = diags.getCustomDiagID(
+            clang::DiagnosticsEngine::Warning,
+            "Argument `-Wextra` was ignored during compilation. Only `-Werror` "
+            "is supported currently.");
+        diags.Report(diagID);
+      } else {
+        const unsigned diagID =
+            diags.getCustomDiagID(clang::DiagnosticsEngine::Error,
+                                  "Only `-Werror` is supported currently.");
+        diags.Report(diagID);
+        break;
+      }
     }
   }
 
diff --git a/flang/test/Driver/werror-all.f90 b/flang/test/Driver/werror-all.f90
new file mode 100644
--- /dev/null
+++ b/flang/test/Driver/werror-all.f90
@@ -0,0 +1,14 @@
+! Ensures that -Werror is read regardless of whether or not other -W
+! flags are present in the CLI args
+
+! RUN: not %flang -std=f2018 -Werror -Wextra %s 2>&1 | FileCheck %s --check-prefix=WRONG 
+! RUN: %flang -std=f2018 -Wextra -Wall %s 2>&1 | FileCheck %s --check-prefix=CHECK-OK
+
+! WRONG: Semantic errors in
+! CHECK-OK: FORALL index variable
+
+program werror_check_all
+  integer :: a(3)
+  forall (j=1:n) a(i) = 1
+end program werror_check_all
+
diff --git a/flang/test/Driver/wextra-ok.f90 b/flang/test/Driver/wextra-ok.f90
new file mode 100644
--- /dev/null
+++ b/flang/test/Driver/wextra-ok.f90
@@ -0,0 +1,11 @@
+! Ensure that supplying -Wextra into flang-new does not raise error
+! The first check should be changed if -Wextra is implemented
+
+! RUN: %flang -std=f2018 -Wextra %s 2>&1 | FileCheck %s --check-prefix=CHECK-OK
+! RUN: not %flang -std=f2018 -Wblah -Wextra %s 2>&1 | FileCheck %s --check-prefix=WRONG
+
+! CHECK-OK: Argument `-Wextra` was ignored during compilation. Only `-Werror` is supported currently.
+! WRONG: Only `-Werror` is supported currently.
+
+program wextra_ok
+end program wextra_ok