Index: clangd/CodeComplete.h
===================================================================
--- clangd/CodeComplete.h
+++ clangd/CodeComplete.h
@@ -177,6 +177,9 @@
   };
   Scores Score;
 
+  /// Indicates if this item is deprecated.
+  bool Deprecated = false;
+
   // Serialize this to an LSP completion item. This is a lossy operation.
   CompletionItem render(const CodeCompleteOptions &) const;
 };
Index: clangd/CodeComplete.cpp
===================================================================
--- clangd/CodeComplete.cpp
+++ clangd/CodeComplete.cpp
@@ -353,6 +353,8 @@
                   return std::tie(X.range.start.line, X.range.start.character) <
                          std::tie(Y.range.start.line, Y.range.start.character);
                 });
+      Completion.Deprecated |=
+          (C.SemaResult->Availability == CXAvailability_Deprecated);
     }
     if (C.IndexResult) {
       Completion.Origin |= C.IndexResult->Origin;
@@ -362,6 +364,7 @@
         Completion.Kind = toCompletionItemKind(C.IndexResult->SymInfo.Kind);
       if (Completion.Name.empty())
         Completion.Name = C.IndexResult->Name;
+      Completion.Deprecated |= C.IndexResult->Deprecated;
     }
 
     // Turn absolute path into a literal string that can be #included.
@@ -1623,6 +1626,7 @@
   LSP.kind = Kind;
   LSP.detail = BundleSize > 1 ? llvm::formatv("[{0} overloads]", BundleSize)
                               : ReturnType;
+  LSP.deprecated = Deprecated;
   if (InsertInclude)
     LSP.detail += "\n" + InsertInclude->Header;
   LSP.documentation = Documentation;
@@ -1654,6 +1658,7 @@
                                              : InsertTextFormat::PlainText;
   if (InsertInclude && InsertInclude->Insertion)
     LSP.additionalTextEdits.push_back(*InsertInclude->Insertion);
+
   return LSP;
 }
 
Index: clangd/Protocol.h
===================================================================
--- clangd/Protocol.h
+++ clangd/Protocol.h
@@ -768,6 +768,9 @@
   /// themselves.
   std::vector<TextEdit> additionalTextEdits;
 
+  /// Indicates if this item is deprecated.
+  bool deprecated = false;
+
   // TODO(krasimir): The following optional fields defined by the language
   // server protocol are unsupported:
   //
Index: clangd/Protocol.cpp
===================================================================
--- clangd/Protocol.cpp
+++ clangd/Protocol.cpp
@@ -517,6 +517,8 @@
     Result["textEdit"] = *CI.textEdit;
   if (!CI.additionalTextEdits.empty())
     Result["additionalTextEdits"] = json::Array(CI.additionalTextEdits);
+  if (CI.deprecated)
+    Result["deprecated"] = CI.deprecated;
   return std::move(Result);
 }
 
Index: clangd/Quality.cpp
===================================================================
--- clangd/Quality.cpp
+++ clangd/Quality.cpp
@@ -167,9 +167,7 @@
 }
 
 void SymbolQualitySignals::merge(const CodeCompletionResult &SemaCCResult) {
-  if (SemaCCResult.Availability == CXAvailability_Deprecated)
-    Deprecated = true;
-
+  Deprecated |= (SemaCCResult.Availability == CXAvailability_Deprecated);
   Category = categorize(SemaCCResult);
 
   if (SemaCCResult.Declaration) {
@@ -180,6 +178,7 @@
 }
 
 void SymbolQualitySignals::merge(const Symbol &IndexResult) {
+  Deprecated |= IndexResult.Deprecated;
   References = std::max(IndexResult.References, References);
   Category = categorize(IndexResult.SymInfo);
   ReservedName = ReservedName || isReserved(IndexResult.Name);
Index: clangd/index/Index.h
===================================================================
--- clangd/index/Index.h
+++ clangd/index/Index.h
@@ -244,7 +244,9 @@
   ///   any definition.
   llvm::SmallVector<IncludeHeaderWithReferences, 1> IncludeHeaders;
 
-  // FIXME: add extra fields for index scoring signals.
+  /// Indicates if the symbol is deprecated.
+  /// FIXME: also add deprecation message and fixit?
+  bool Deprecated = false;
 };
 llvm::raw_ostream &operator<<(llvm::raw_ostream &OS, const Symbol &S);
 
Index: clangd/index/SymbolCollector.cpp
===================================================================
--- clangd/index/SymbolCollector.cpp
+++ clangd/index/SymbolCollector.cpp
@@ -535,6 +535,7 @@
     S.IncludeHeaders.emplace_back(Include, 1);
 
   S.Origin = Opts.Origin;
+  S.Deprecated = ND.getAvailability() == AR_Deprecated;
   Symbols.insert(S);
   return Symbols.find(S.ID);
 }
Index: unittests/clangd/CodeCompleteTests.cpp
===================================================================
--- unittests/clangd/CodeCompleteTests.cpp
+++ unittests/clangd/CodeCompleteTests.cpp
@@ -77,6 +77,7 @@
   return Contains(AllOf(Named(std::move(Name)), Kind(K)));
 }
 MATCHER(IsDocumented, "") { return !arg.Documentation.empty(); }
+MATCHER(Deprecated, "") { return arg.Deprecated; }
 
 std::unique_ptr<SymbolIndex> memIndex(std::vector<Symbol> Symbols) {
   SymbolSlab::Builder Slab;
@@ -1355,6 +1356,7 @@
   C.Kind = CompletionItemKind::Method;
   C.Score.Total = 1.0;
   C.Origin = SymbolOrigin::AST | SymbolOrigin::Static;
+  C.Deprecated = true;
 
   CodeCompleteOptions Opts;
   Opts.IncludeIndicator.Insert = "^";
@@ -1370,6 +1372,7 @@
   EXPECT_EQ(R.documentation, "This is x().");
   EXPECT_THAT(R.additionalTextEdits, IsEmpty());
   EXPECT_EQ(R.sortText, sortText(1.0, "x"));
+  EXPECT_TRUE(R.deprecated);
 
   Opts.EnableSnippets = true;
   R = C.render(Opts);
@@ -1882,6 +1885,18 @@
           AllOf(Named("Func"), HasInclude("\"foo.h\""), Not(InsertInclude()))));
 }
 
+TEST(CompletionTest, DeprecatedResults) {
+  std::string Body = R"cpp(
+    void TestClangd();
+    void TestClangc() __attribute__((deprecated("", "")));
+  )cpp";
+
+  EXPECT_THAT(
+      completions(Body + "int main() { TestClang^ }").Completions,
+      UnorderedElementsAre(AllOf(Named("TestClangd"), Not(Deprecated())),
+                           AllOf(Named("TestClangc"), Deprecated())));
+}
+
 } // namespace
 } // namespace clangd
 } // namespace clang
Index: unittests/clangd/QualityTests.cpp
===================================================================
--- unittests/clangd/QualityTests.cpp
+++ unittests/clangd/QualityTests.cpp
@@ -59,7 +59,7 @@
   F.References = 24; // TestTU doesn't count references, so fake it.
   Quality = {};
   Quality.merge(F);
-  EXPECT_FALSE(Quality.Deprecated); // FIXME: Include deprecated bit in index.
+  EXPECT_TRUE(Quality.Deprecated);
   EXPECT_FALSE(Quality.ReservedName);
   EXPECT_EQ(Quality.References, 24u);
   EXPECT_EQ(Quality.Category, SymbolQualitySignals::Function);