diff --git a/toolchain/check/cpp/export.cpp b/toolchain/check/cpp/export.cpp
index 7d54ac666f3e..f9b27a9776d4 100644
--- a/toolchain/check/cpp/export.cpp
+++ b/toolchain/check/cpp/export.cpp
@@ -8,6 +8,7 @@
 #include <string_view>
 
 #include "clang/AST/ASTConsumer.h"
+#include "clang/Lex/Preprocessor.h"
 #include "clang/Sema/EnterExpressionEvaluationContext.h"
 #include "clang/Sema/Sema.h"
 #include "llvm/Support/Casting.h"
@@ -251,11 +252,25 @@ static auto CreateCppFieldDecl(Context& context,
   return cpp_field_decl;
 }
 
-auto ExportAllFieldsToCpp(Context& context, SemIR::Class& class_info) -> void {
-  if (class_info.fields_exported) {
-    return;
-  }
+// Create an invalid `clang::FieldDecl`. This is only used as an error marker
+// to indicate that a Carbon field has already been unsuccessfully exported.
+static auto CreateInvalidFieldDecl(Context& context,
+                                   clang::DeclContext* decl_context)
+    -> clang::FieldDecl* {
+  clang::SourceLocation clang_loc;
+  auto* identifier_info =
+      context.clang_sema().getPreprocessor().getIdentifierInfo("invalid_field");
+  auto cpp_type = context.ast_context().IntTy;
+  auto* field_decl = clang::FieldDecl::Create(
+      context.ast_context(), decl_context, /*StartLoc=*/clang_loc,
+      /*IdLoc=*/clang_loc, identifier_info, cpp_type, /*TInfo=*/nullptr,
+      /*BW=*/nullptr,
+      /*Mutable=*/true, clang::ICIS_NoInit);
+  field_decl->setInvalidDecl();
+  return field_decl;
+}
 
+auto ExportAllFieldsToCpp(Context& context, SemIR::Class& class_info) -> void {
   const auto& class_scope = context.name_scopes().Get(class_info.scope_id);
 
   for (const auto& struct_field :
@@ -266,6 +281,13 @@ auto ExportAllFieldsToCpp(Context& context, SemIR::Class& class_info) -> void {
       continue;
     }
 
+    // Return early if the field is already exported. Since fields are always
+    // exported as a group, this indicates all fields have been exported so
+    // there's no need to continue to the rest.
+    if (context.clang_decls().Lookup(class_field->inst_id)) {
+      return;
+    }
+
     // Map the parent scope into the C++ AST.
     auto* decl_context = ExportNameScopeToCpp(
         context, SemIR::LocId(class_field->inst_id), class_info.scope_id);
@@ -276,16 +298,19 @@ auto ExportAllFieldsToCpp(Context& context, SemIR::Class& class_info) -> void {
     auto* cpp_field_decl = CreateCppFieldDecl(
         context, class_scope, cast<clang::CXXRecordDecl>(decl_context),
         class_field->inst_id, class_field->inst);
+
+    // If the field cannot be exported, create an invalid `FieldDecl` to store
+    // in `clang_decls`. This marks the field as unsuccessfully exported, so
+    // that we know not to attempt export again (which could create duplicate
+    // error diagnostics).
     if (!cpp_field_decl) {
-      continue;
+      cpp_field_decl = CreateInvalidFieldDecl(context, decl_context);
     }
 
     // Create and store the `ClangDeclId`.
     auto key = SemIR::ClangDeclKey::ForNonFunctionDecl(cpp_field_decl);
     context.clang_decls().Add({.key = key, .inst_id = class_field->inst_id});
   }
-
-  class_info.fields_exported = true;
 }
 
 auto ExportFieldToCpp(Context& context, SemIR::InstId field_inst_id,
@@ -303,7 +328,9 @@ auto ExportFieldToCpp(Context& context, SemIR::InstId field_inst_id,
 
   // Get the exported `clang::FieldDecl`.
   if (const auto* clang_decl = context.clang_decls().Lookup(field_inst_id)) {
-    return cast<clang::FieldDecl>(clang_decl->decl());
+    if (!clang_decl->decl()->isInvalidDecl()) {
+      return cast<clang::FieldDecl>(clang_decl->decl());
+    }
   }
   return nullptr;
 }
diff --git a/toolchain/sem_ir/class.h b/toolchain/sem_ir/class.h
index 476d884b861c..29221f40dd4f 100644
--- a/toolchain/sem_ir/class.h
+++ b/toolchain/sem_ir/class.h
@@ -46,9 +46,6 @@ struct ClassFields {
   // Whether this class or any base class has at least one virtual function.
   bool is_dynamic = false;
 
-  // Whether the class's fields have been exported to C++.
-  bool fields_exported = false;
-
   // The following members are set at the `{` of the class definition.
 
   // The class scope.