diff --git a/clang-tools-extra/clangd/Diagnostics.cpp b/clang-tools-extra/clangd/Diagnostics.cpp
--- a/clang-tools-extra/clangd/Diagnostics.cpp
+++ b/clang-tools-extra/clangd/Diagnostics.cpp
@@ -374,7 +374,12 @@
   } else if (UnusedDiags->contains(D.ID)) {
     D.Tags.push_back(DiagnosticTag::Unnecessary);
   }
-  // FIXME: Set tags for tidy-based diagnostics too.
+  if (D.Source == Diag::ClangTidy) {
+    if (llvm::StringRef(D.Name).starts_with("misc-unused-"))
+      D.Tags.push_back(DiagnosticTag::Unnecessary);
+    if (llvm::StringRef(D.Name).starts_with("modernize-"))
+      D.Tags.push_back(DiagnosticTag::Deprecated);
+  }
 }
 } // namespace
 
@@ -566,7 +571,6 @@
 
   // Fill in name/source now that we have all the context needed to map them.
   for (auto &Diag : Output) {
-    setTags(Diag);
     if (const char *ClangDiag = getDiagnosticCode(Diag.ID)) {
       // Warnings controlled by -Wfoo are better recognized by that name.
       StringRef Warning = DiagnosticIDs::getWarningOptionForDiag(Diag.ID);
@@ -580,9 +584,7 @@
         Diag.Name = std::string(Name);
       }
       Diag.Source = Diag::Clang;
-      continue;
-    }
-    if (Tidy != nullptr) {
+    } else if (Tidy != nullptr) {
       std::string TidyDiag = Tidy->getCheckName(Diag.ID);
       if (!TidyDiag.empty()) {
         Diag.Name = std::move(TidyDiag);
@@ -600,9 +602,9 @@
           CleanMessage(Note.Message);
         for (auto &Fix : Diag.Fixes)
           CleanMessage(Fix.Message);
-        continue;
       }
     }
+    setTags(Diag);
   }
   // Deduplicate clang-tidy diagnostics -- some clang-tidy checks may emit
   // duplicated messages due to various reasons (e.g. the check doesn't handle
diff --git a/clang-tools-extra/clangd/unittests/DiagnosticsTests.cpp b/clang-tools-extra/clangd/unittests/DiagnosticsTests.cpp
--- a/clang-tools-extra/clangd/unittests/DiagnosticsTests.cpp
+++ b/clang-tools-extra/clangd/unittests/DiagnosticsTests.cpp
@@ -1851,6 +1851,17 @@
                         withTag(DiagnosticTag::Unnecessary)),
                   AllOf(Diag(Test.range("deprecated"), "'bar' is deprecated"),
                         withTag(DiagnosticTag::Deprecated))));
+
+  Test = Annotations(R"cpp(
+    $typedef[[typedef int INT]];
+  )cpp");
+  TU.Code = Test.code();
+  TU.ClangTidyProvider = addTidyChecks("modernize-use-using");
+  EXPECT_THAT(
+      *TU.build().getDiagnostics(),
+      UnorderedElementsAre(
+          AllOf(Diag(Test.range("typedef"), "use 'using' instead of 'typedef'"),
+                withTag(DiagnosticTag::Deprecated))));
 }
 
 TEST(DiagnosticsTest, IncludeCleaner) {