Index: clangd/ClangdServer.cpp
===================================================================
--- clangd/ClangdServer.cpp
+++ clangd/ClangdServer.cpp
@@ -534,6 +534,7 @@
   // Inject the resource dir.
   // FIXME: Don't overwrite it if it's already there.
   C->CommandLine.push_back("-resource-dir=" + ResourceDir);
+  C->CommandLine.push_back("-Wdeprecated-declarations");
   return std::move(*C);
 }
 
Index: clangd/Diagnostics.cpp
===================================================================
--- clangd/Diagnostics.cpp
+++ clangd/Diagnostics.cpp
@@ -292,10 +292,11 @@
     D.Message = Message.str();
     D.InsideMainFile = InsideMainFile;
     D.File = Info.getSourceManager().getFilename(Info.getLocation());
-    D.Severity = DiagLevel;
     D.Category = DiagnosticIDs::getCategoryNameFromID(
                      DiagnosticIDs::getCategoryNumberForDiag(Info.getID()))
                      .str();
+    D.Severity =
+        D.Category == "Deprecations" ? DiagnosticsEngine::Note : DiagLevel;
     return D;
   };
 
Index: unittests/clangd/ClangdUnitTests.cpp
===================================================================
--- unittests/clangd/ClangdUnitTests.cpp
+++ unittests/clangd/ClangdUnitTests.cpp
@@ -38,6 +38,13 @@
   return arg.Range == Range && arg.Message == Message;
 }
 
+MATCHER_P3(Diag, Range, Message, Severity,
+           "Diag at " + llvm::to_string(Range) + " = [" + Message +
+               "] with Severity:" + llvm::to_string(Severity)) {
+  return arg.Range == Range && arg.Message == Message &&
+         arg.Severity == Severity;
+}
+
 MATCHER_P3(Fix, Range, Replacement, Message,
            "Fix " + llvm::to_string(Range) + " => " +
                testing::PrintToString(Replacement) + " = [" + Message + "]") {
@@ -220,6 +227,46 @@
   }
 }
 
+TEST(DiagnosticsTest, DiagnosticDeprecated) {
+  Annotations Test(R"cpp(
+    void foo() __attribute__(($foodeprecation[[deprecated]]));
+    class A {
+    public:
+      int x __attribute__(($xdeprecation[[deprecated]]));
+    };
+    int main() {
+      $foo[[foo]]();
+      return A().$x[[x]];
+    }
+  )cpp");
+  EXPECT_THAT(
+      TestTU::withCode(Test.code()).build().getDiagnostics(),
+      ElementsAre(
+          AllOf(Diag(Test.range("foo"), "'foo' is deprecated",
+                     DiagnosticsEngine::Note),
+                WithNote(
+                    Diag(Test.range("foodeprecation"),
+                         "'foo' has been explicitly marked deprecated here"))),
+          AllOf(Diag(Test.range("x"), "'x' is deprecated",
+                     DiagnosticsEngine::Note),
+                WithNote(
+                    Diag(Test.range("xdeprecation"),
+                         "'x' has been explicitly marked deprecated here")))));
+}
+
+TEST(DiagnosticsTest, DiagnosticDeprecatedWithFix) {
+  Annotations Test(R"cpp(
+    void bar();
+    void foo() __attribute__((deprecated("", "bar")));
+    int main() {
+      $deprecated[[foo]]();
+    }
+  )cpp");
+  EXPECT_THAT(TestTU::withCode(Test.code()).build().getDiagnostics(),
+              ElementsAre(WithFix(Fix(Test.range("deprecated"), "bar",
+                                      "change 'foo' to 'bar'"))));
+}
+
 } // namespace
 } // namespace clangd
 } // namespace clang