diff --git a/pkg/analysis_server/lib/src/lsp/handlers/handler_completion_resolve.dart b/pkg/analysis_server/lib/src/lsp/handlers/handler_completion_resolve.dart
index 99305e12cd1..b01b3477f1e 100644
--- a/pkg/analysis_server/lib/src/lsp/handlers/handler_completion_resolve.dart
+++ b/pkg/analysis_server/lib/src/lsp/handlers/handler_completion_resolve.dart
@@ -150,7 +150,7 @@ class CompletionResolveHandler
         return success(CompletionItem(
           label: item.label,
           kind: item.kind,
-          tags: null, // TODO(dantup): CompletionItemTags (eg. deprecated)
+          tags: item.tags,
           detail: data.displayUri != null && thisFilesChanges.isNotEmpty
               ? "Auto import from '${data.displayUri}'\n\n${item.detail ?? ''}"
                   .trim()
diff --git a/pkg/analysis_server/lib/src/lsp/mapping.dart b/pkg/analysis_server/lib/src/lsp/mapping.dart
index c36554ec00e..5685c5d5a88 100644
--- a/pkg/analysis_server/lib/src/lsp/mapping.dart
+++ b/pkg/analysis_server/lib/src/lsp/mapping.dart
@@ -224,8 +224,12 @@ lsp.CompletionItem declarationToCompletionItem(
       label = declaration.name;
   }
 
-  final useDeprecated =
+  final supportsDeprecatedFlag =
       completionCapabilities?.completionItem?.deprecatedSupport == true;
+  final supportedTags =
+      completionCapabilities?.completionItem?.tagSupport?.valueSet ?? const [];
+  final supportsDeprecatedTag =
+      supportedTags.contains(lsp.CompletionItemTag.Deprecated);
 
   final completionKind = declarationKindToCompletionItemKind(
       supportedCompletionItemKinds, declaration.kind);
@@ -243,10 +247,16 @@ lsp.CompletionItem declarationToCompletionItem(
   return lsp.CompletionItem(
     label: label,
     kind: completionKind,
-    tags: null, // TODO(dantup): CompletionItemTags
-    detail: getDeclarationCompletionDetail(
-        declaration, completionKind, useDeprecated),
-    deprecated: useDeprecated && declaration.isDeprecated ? true : null,
+    tags: supportedTags.isNotEmpty
+        ? [
+            if (supportsDeprecatedTag && declaration.isDeprecated)
+              lsp.CompletionItemTag.Deprecated
+          ]
+        : null,
+    detail: getDeclarationCompletionDetail(declaration, completionKind,
+        supportsDeprecatedFlag || supportsDeprecatedTag),
+    deprecated:
+        supportsDeprecatedFlag && declaration.isDeprecated ? true : null,
     // Relevance is a number, highest being best. LSP does text sort so subtract
     // from a large number so that a text sort will result in the correct order.
     // 555 -> 999455
@@ -723,8 +733,12 @@ lsp.CompletionItem toCompletionItem(
     }
   }
 
-  final useDeprecated =
+  final supportsDeprecatedFlag =
       completionCapabilities?.completionItem?.deprecatedSupport == true;
+  final supportedTags =
+      completionCapabilities?.completionItem?.tagSupport?.valueSet ?? const [];
+  final supportsDeprecatedTag =
+      supportedTags.contains(lsp.CompletionItemTag.Deprecated);
   final formats = completionCapabilities?.completionItem?.documentationFormat;
   final supportsSnippets =
       completionCapabilities?.completionItem?.snippetSupport == true;
@@ -751,11 +765,17 @@ lsp.CompletionItem toCompletionItem(
   return lsp.CompletionItem(
     label: label,
     kind: completionKind,
-    tags: null, // TODO(dantup): CompletionItemTags
-    detail: getCompletionDetail(suggestion, completionKind, useDeprecated),
+    tags: supportedTags.isNotEmpty
+        ? [
+            if (supportsDeprecatedTag && suggestion.isDeprecated)
+              lsp.CompletionItemTag.Deprecated
+          ]
+        : null,
+    detail: getCompletionDetail(suggestion, completionKind,
+        supportsDeprecatedFlag || supportsDeprecatedTag),
     documentation:
         asStringOrMarkupContent(formats, cleanDartdoc(suggestion.docComplete)),
-    deprecated: useDeprecated && suggestion.isDeprecated ? true : null,
+    deprecated: supportsDeprecatedFlag && suggestion.isDeprecated ? true : null,
     // Relevance is a number, highest being best. LSP does text sort so subtract
     // from a large number so that a text sort will result in the correct order.
     // 555 -> 999455
diff --git a/pkg/analysis_server/test/lsp/completion_test.dart b/pkg/analysis_server/test/lsp/completion_test.dart
index 66df9f177d6..9d045cf6461 100644
--- a/pkg/analysis_server/test/lsp/completion_test.dart
+++ b/pkg/analysis_server/test/lsp/completion_test.dart
@@ -300,7 +300,7 @@ class CompletionTest extends AbstractLspAnalysisServerTest {
     expect(item.detail.toLowerCase(), contains('deprecated'));
   }
 
-  Future<void> test_isDeprecated_supported() async {
+  Future<void> test_isDeprecated_supportedFlag() async {
     final content = '''
     class MyClass {
       @deprecated
@@ -314,7 +314,7 @@ class CompletionTest extends AbstractLspAnalysisServerTest {
     ''';
 
     await initialize(
-        textDocumentCapabilities: withCompletionItemDeprecatedSupport(
+        textDocumentCapabilities: withCompletionItemDeprecatedFlagSupport(
             emptyTextDocumentClientCapabilities));
     await openFile(mainFileUri, withoutMarkers(content));
     final res = await getCompletion(mainFileUri, positionFromMarker(content));
@@ -326,6 +326,32 @@ class CompletionTest extends AbstractLspAnalysisServerTest {
     expect(item.detail, isNot(contains('deprecated')));
   }
 
+  Future<void> test_isDeprecated_supportedTag() async {
+    final content = '''
+    class MyClass {
+      @deprecated
+      String abcdefghij;
+    }
+
+    main() {
+      MyClass a;
+      a.abc^
+    }
+    ''';
+
+    await initialize(
+        textDocumentCapabilities: withCompletionItemTagSupport(
+            emptyTextDocumentClientCapabilities,
+            [CompletionItemTag.Deprecated]));
+    await openFile(mainFileUri, withoutMarkers(content));
+    final res = await getCompletion(mainFileUri, positionFromMarker(content));
+    final item = res.singleWhere((c) => c.label == 'abcdefghij');
+    expect(item.tags, contains(CompletionItemTag.Deprecated));
+    // If the client says it supports the deprecated tag, we should not show
+    // deprecated in the details.
+    expect(item.detail, isNot(contains('deprecated')));
+  }
+
   Future<void> test_namedArg_plainText() async {
     final content = '''
     class A { const A({int one}); }
diff --git a/pkg/analysis_server/test/lsp/server_abstract.dart b/pkg/analysis_server/test/lsp/server_abstract.dart
index 795c5b7e241..9de60d074dc 100644
--- a/pkg/analysis_server/test/lsp/server_abstract.dart
+++ b/pkg/analysis_server/test/lsp/server_abstract.dart
@@ -227,7 +227,7 @@ mixin ClientCapabilitiesHelperMixin {
     });
   }
 
-  TextDocumentClientCapabilities withCompletionItemDeprecatedSupport(
+  TextDocumentClientCapabilities withCompletionItemDeprecatedFlagSupport(
     TextDocumentClientCapabilities source,
   ) {
     return extendTextDocumentCapabilities(source, {
@@ -260,6 +260,19 @@ mixin ClientCapabilitiesHelperMixin {
     });
   }
 
+  TextDocumentClientCapabilities withCompletionItemTagSupport(
+    TextDocumentClientCapabilities source,
+    List<CompletionItemTag> tags,
+  ) {
+    return extendTextDocumentCapabilities(source, {
+      'completion': {
+        'completionItem': {
+          'tagSupport': {'valueSet': tags.map((k) => k.toJson()).toList()}
+        }
+      }
+    });
+  }
+
   ClientCapabilitiesWorkspace withConfigurationSupport(
     ClientCapabilitiesWorkspace source,
   ) {