diff --git a/flang/include/flang/Support/Fortran-features.h b/flang/include/flang/Support/Fortran-features.h
index 83a75b0efcb55..89d1dba7a2dc8 100644
--- a/flang/include/flang/Support/Fortran-features.h
+++ b/flang/include/flang/Support/Fortran-features.h
@@ -73,7 +73,7 @@ ENUM_CLASS(UsageWarning, Portability, PointerToUndefinable,
     ZeroDoStep, UnusedForallIndex, OpenMPUsage, DataLength, IgnoredDirective,
     HomonymousSpecific, HomonymousResult, IgnoredIntrinsicFunctionType,
     PreviousScalarUse, RedeclaredInaccessibleComponent, ImplicitShared,
-    IndexVarRedefinition, IncompatibleImplicitInterfaces,
+    IndexVarRedefinition, IncompatibleImplicitInterfaces, CdefinedInit,
     VectorSubscriptFinalization, UndefinedFunctionResult, UselessIomsg,
     MismatchingDummyProcedure, SubscriptedEmptyArray, UnsignedLiteralTruncation,
     CompatibleDeclarationsFromDistinctModules,
diff --git a/flang/lib/Semantics/resolve-names.cpp b/flang/lib/Semantics/resolve-names.cpp
index d0d3b0e1caa5a..cdd8d6ff2f60e 100644
--- a/flang/lib/Semantics/resolve-names.cpp
+++ b/flang/lib/Semantics/resolve-names.cpp
@@ -9118,6 +9118,9 @@ void DeclarationVisitor::NonPointerInitialization(
         if (details->init()) {
           SayWithDecl(name, *name.symbol,
               "'%s' has already been initialized"_err_en_US);
+        } else if (details->isCDefined()) {
+          context().Warn(common::UsageWarning::CdefinedInit, name.source,
+              "CDEFINED variable should not have an initializer"_warn_en_US);
         } else if (IsAllocatable(ultimate)) {
           Say(name, "Allocatable object '%s' cannot be initialized"_err_en_US);
         } else if (ultimate.owner().IsParameterizedDerivedType()) {
diff --git a/flang/test/Semantics/cdefined.f90 b/flang/test/Semantics/cdefined.f90
new file mode 100644
index 0000000000000..84103ce661d0b
--- /dev/null
+++ b/flang/test/Semantics/cdefined.f90
@@ -0,0 +1,6 @@
+! RUN: %python %S/test_errors.py %s %flang_fc1 -pedantic -Werror
+module m
+  use iso_c_binding
+  !WARNING: CDEFINED variable should not have an initializer [-Wcdefined-init]
+  integer(c_int), bind(C, name='c_global', CDEFINED) :: c  = 42
+end