diff --git a/clang-tools-extra/clang-tidy/modernize/ConcatNestedNamespacesCheck.cpp b/clang-tools-extra/clang-tidy/modernize/ConcatNestedNamespacesCheck.cpp
--- a/clang-tools-extra/clang-tidy/modernize/ConcatNestedNamespacesCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/ConcatNestedNamespacesCheck.cpp
@@ -31,8 +31,9 @@
   return Lexer::getSourceText(TextRange, Sources, LangOpts);
 }
 
-static bool anonymousOrInlineNamespace(const NamespaceDecl &ND) {
-  return ND.isAnonymousNamespace() || ND.isInlineNamespace();
+static bool unsupportedNamespace(const NamespaceDecl &ND) {
+  return ND.isAnonymousNamespace() || ND.isInlineNamespace() ||
+         !ND.attrs().empty();
 }
 
 static bool singleNamedNamespaceChild(const NamespaceDecl &ND) {
@@ -41,7 +42,7 @@
     return false;
 
   const auto *ChildNamespace = dyn_cast<const NamespaceDecl>(*Decls.begin());
-  return ChildNamespace && !anonymousOrInlineNamespace(*ChildNamespace);
+  return ChildNamespace && !unsupportedNamespace(*ChildNamespace);
 }
 
 static bool alreadyConcatenated(std::size_t NumCandidates,
@@ -166,7 +167,7 @@
   if (!locationsInSameFile(Sources, ND.getBeginLoc(), ND.getRBraceLoc()))
     return;
 
-  if (anonymousOrInlineNamespace(ND))
+  if (unsupportedNamespace(ND))
     return;
 
   Namespaces.push_back(&ND);
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -301,9 +301,10 @@
   <clang-tidy/checks/google/readability-avoid-underscore-in-googletest-name>` when using
   ``DISABLED_`` in the test suite name.
 
-- Fixed an issue in :doc:`modernize-concat-nested-namespaces
-  <clang-tidy/checks/modernize/concat-nested-namespaces>` when using macro between
-  namespace declarations could result incorrect fix.
+- Improved :doc:`modernize-concat-nested-namespaces
+  <clang-tidy/checks/modernize/concat-nested-namespaces>` to fix incorrect fixes when 
+  using macro between namespace declarations and false positive when using namespace 
+  with attributes.
 
 - Fixed a false positive in :doc:`performance-no-automatic-move
   <clang-tidy/checks/performance/no-automatic-move>` when warning would be
diff --git a/clang-tools-extra/test/clang-tidy/checkers/modernize/concat-nested-namespaces.cpp b/clang-tools-extra/test/clang-tidy/checkers/modernize/concat-nested-namespaces.cpp
--- a/clang-tools-extra/test/clang-tidy/checkers/modernize/concat-nested-namespaces.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/modernize/concat-nested-namespaces.cpp
@@ -21,11 +21,17 @@
 } // namespace n2
 
 namespace n5 {
-inline namespace n6 {
+inline namespace inline_ns {
 void t();
-}
+} // namespace inline_ns
 } // namespace n5
 
+namespace n6 {
+namespace [[deprecated]] attr_ns {
+void t();
+} // namespace attr_ns
+} // namespace n6
+
 namespace n7 {
 void t();