diff --git a/clang-tools-extra/clangd/refactor/Rename.h b/clang-tools-extra/clangd/refactor/Rename.h
--- a/clang-tools-extra/clangd/refactor/Rename.h
+++ b/clang-tools-extra/clangd/refactor/Rename.h
@@ -51,6 +51,7 @@
 /// Generates rename edits that replaces all given occurrences with the
 /// NewName.
 /// Exposed for testing only.
+/// REQUIRED: Occurrences is sorted and doesn't have duplicated ranges.
 llvm::Expected<Edit> buildRenameEdit(llvm::StringRef AbsFilePath,
                                      llvm::StringRef InitialCode,
                                      std::vector<Range> Occurrences,
@@ -65,6 +66,7 @@
 ///
 /// The API assumes that Indexed contains only named occurrences (each
 /// occurrence has the same length).
+/// REQUIRED: Indexed is sorted.
 llvm::Optional<std::vector<Range>>
 adjustRenameRanges(llvm::StringRef DraftCode, llvm::StringRef Identifier,
                    std::vector<Range> Indexed, const LangOptions &LangOpts);
diff --git a/clang-tools-extra/clangd/refactor/Rename.cpp b/clang-tools-extra/clangd/refactor/Rename.cpp
--- a/clang-tools-extra/clangd/refactor/Rename.cpp
+++ b/clang-tools-extra/clangd/refactor/Rename.cpp
@@ -319,7 +319,12 @@
                       RenameDecl.getQualifiedNameAsString()),
         llvm::inconvertibleErrorCode());
   }
-
+  // Sort and deduplicate the results, in case that index returns duplications.
+  for (auto &FileAndOccurrences : AffectedFiles) {
+    auto &Ranges = FileAndOccurrences.getValue();
+    llvm::sort(Ranges);
+    Ranges.erase(std::unique(Ranges.begin(), Ranges.end()), Ranges.end());
+  }
   return AffectedFiles;
 }
 
@@ -514,7 +519,11 @@
                                      llvm::StringRef InitialCode,
                                      std::vector<Range> Occurrences,
                                      llvm::StringRef NewName) {
-  llvm::sort(Occurrences);
+  assert(std::is_sorted(Occurrences.begin(), Occurrences.end()));
+  assert(std::unique(Occurrences.begin(), Occurrences.end()) ==
+             Occurrences.end() &&
+         "Occurrences must be unique");
+
   // These two always correspond to the same position.
   Position LastPos{0, 0};
   size_t LastOffset = 0;
@@ -574,9 +583,9 @@
 adjustRenameRanges(llvm::StringRef DraftCode, llvm::StringRef Identifier,
                    std::vector<Range> Indexed, const LangOptions &LangOpts) {
   assert(!Indexed.empty());
+  assert(std::is_sorted(Indexed.begin(), Indexed.end()));
   std::vector<Range> Lexed =
       collectIdentifierRanges(Identifier, DraftCode, LangOpts);
-  llvm::sort(Indexed);
   llvm::sort(Lexed);
   return getMappedRanges(Indexed, Lexed);
 }
diff --git a/clang-tools-extra/clangd/unittests/RenameTests.cpp b/clang-tools-extra/clangd/unittests/RenameTests.cpp
--- a/clang-tools-extra/clangd/unittests/RenameTests.cpp
+++ b/clang-tools-extra/clangd/unittests/RenameTests.cpp
@@ -30,6 +30,18 @@
 using testing::UnorderedElementsAre;
 using testing::UnorderedElementsAreArray;
 
+// Covnert a Range to a Ref.
+Ref refWithRange(const clangd::Range &Range, const std::string &URI) {
+  Ref Result;
+  Result.Kind = RefKind::Reference;
+  Result.Location.Start.setLine(Range.start.line);
+  Result.Location.Start.setColumn(Range.start.character);
+  Result.Location.End.setLine(Range.end.line);
+  Result.Location.End.setColumn(Range.end.character);
+  Result.Location.FileURI = URI.c_str();
+  return Result;
+}
+
 // Build a RefSlab from all marked ranges in the annotation. The ranges are
 // assumed to associate with the given SymbolName.
 std::unique_ptr<RefSlab> buildRefSlab(const Annotations &Code,
@@ -40,17 +52,9 @@
   TU.HeaderCode = Code.code();
   auto Symbols = TU.headerSymbols();
   const auto &SymbolID = findSymbol(Symbols, SymbolName).ID;
-  for (const auto &Range : Code.ranges()) {
-    Ref R;
-    R.Kind = RefKind::Reference;
-    R.Location.Start.setLine(Range.start.line);
-    R.Location.Start.setColumn(Range.start.character);
-    R.Location.End.setLine(Range.end.line);
-    R.Location.End.setColumn(Range.end.character);
-    auto U = URI::create(Path).toString();
-    R.Location.FileURI = U.c_str();
-    Builder.insert(SymbolID, R);
-  }
+  std::string PathURI = URI::create(Path).toString();
+  for (const auto &Range : Code.ranges())
+    Builder.insert(SymbolID, refWithRange(Range, PathURI));
 
   return std::make_unique<RefSlab>(std::move(Builder).build());
 }
@@ -664,6 +668,54 @@
               testing::HasSubstr("too many occurrences"));
 }
 
+TEST(CrossFileRenameTests, DeduplicateRefsFromIndex) {
+  auto MainCode = Annotations("int [[^x]] = 2;");
+  auto MainFilePath = testPath("main.cc");
+  auto BarCode = Annotations("int [[x]];");
+  auto BarPath = testPath("bar.cc");
+  auto TU = TestTU::withCode(MainCode.code());
+  // Set a file "bar.cc" on disk.
+  TU.AdditionalFiles["bar.cc"] = BarCode.code();
+  auto AST = TU.build();
+  std::string BarPathURI = URI::create(BarPath).toString();
+  Ref XRefInBarCC = refWithRange(BarCode.range(), BarPathURI);
+  // The index will return duplicated refs, our code should be robost to handle
+  // it.
+  class DuplicatedXRefIndex : public SymbolIndex {
+  public:
+    DuplicatedXRefIndex(const Ref &ReturnedRef) : ReturnedRef(ReturnedRef) {}
+    bool refs(const RefsRequest &Req,
+              llvm::function_ref<void(const Ref &)> Callback) const override {
+      // Return two duplicated refs.
+      Callback(ReturnedRef);
+      Callback(ReturnedRef);
+      return false;
+    }
+
+    bool fuzzyFind(const FuzzyFindRequest &,
+                   llvm::function_ref<void(const Symbol &)>) const override {
+      return false;
+    }
+    void lookup(const LookupRequest &,
+                llvm::function_ref<void(const Symbol &)>) const override {}
+
+    void relations(const RelationsRequest &,
+                   llvm::function_ref<void(const SymbolID &, const Symbol &)>)
+        const override {}
+    size_t estimateMemoryUsage() const override { return 0; }
+    Ref ReturnedRef;
+  } DIndex(XRefInBarCC);
+  llvm::StringRef NewName = "newName";
+  auto Results = rename({MainCode.point(), NewName, AST, MainFilePath, &DIndex,
+                         /*CrossFile=*/true});
+  ASSERT_TRUE(bool(Results)) << Results.takeError();
+  EXPECT_THAT(
+      applyEdits(std::move(*Results)),
+      UnorderedElementsAre(
+          Pair(Eq(BarPath), Eq(expectedResult(BarCode, NewName))),
+          Pair(Eq(MainFilePath), Eq(expectedResult(MainCode, NewName)))));
+}
+
 TEST(CrossFileRenameTests, WithUpToDateIndex) {
   MockCompilationDatabase CDB;
   CDB.ExtraClangFlags = {"-xc++"};