diff --git a/clang-tools-extra/clangd/FindSymbols.cpp b/clang-tools-extra/clangd/FindSymbols.cpp
--- a/clang-tools-extra/clangd/FindSymbols.cpp
+++ b/clang-tools-extra/clangd/FindSymbols.cpp
@@ -247,6 +247,10 @@
   enum class VisitKind { No, OnlyDecl, OnlyChildren, DeclAndChildren };
 
   void traverseDecl(Decl *D, std::vector<DocumentSymbol> &Results) {
+    // Skip symbols which do not originate from the main file.
+    if (!isInsideMainFile(D->getLocation(), AST.getSourceManager()))
+      return;
+
     if (auto *Templ = llvm::dyn_cast<TemplateDecl>(D)) {
       // TemplatedDecl might be null, e.g. concepts.
       if (auto *TD = Templ->getTemplatedDecl())
diff --git a/clang-tools-extra/clangd/unittests/FindSymbolsTests.cpp b/clang-tools-extra/clangd/unittests/FindSymbolsTests.cpp
--- a/clang-tools-extra/clangd/unittests/FindSymbolsTests.cpp
+++ b/clang-tools-extra/clangd/unittests/FindSymbolsTests.cpp
@@ -489,6 +489,19 @@
               ElementsAre(WithName("foo"), WithName("Foo")));
 }
 
+TEST(DocumentSymbols, InMainFile) {
+  TestTU TU;
+  TU.AdditionalFiles["bar.h"] = "void bar();";
+  TU.Code = R"cpp(
+      namespace ns {
+      #include "bar.h"
+      void foo();
+      })cpp";
+
+  EXPECT_THAT(getSymbols(TU.build()),
+              ElementsAre(AllOf(WithName("ns"), Children(WithName("foo")))));
+}
+
 TEST(DocumentSymbols, NoLocals) {
   TestTU TU;
   TU.Code = R"cpp(