diff --git a/packages/plugin-ext/src/common/plugin-api-rpc-model.ts b/packages/plugin-ext/src/common/plugin-api-rpc-model.ts
index 82b712f9c1f4e..64aa35a6c38f5 100644
--- a/packages/plugin-ext/src/common/plugin-api-rpc-model.ts
+++ b/packages/plugin-ext/src/common/plugin-api-rpc-model.ts
@@ -16,6 +16,7 @@
 
 import * as theia from '@theia/plugin';
 import { UriComponents } from './uri-components';
+import { CompletionItemTag } from '../plugin/types-impl';
 
 // Should contains internal Plugin API types
 
@@ -114,6 +115,9 @@ export interface Completion {
     commitCharacters?: string[];
     additionalTextEdits?: SingleEditOperation[];
     command?: Command;
+    tags?: CompletionItemTag[];
+    /** @deprecated use tags instead. */
+    deprecated?: boolean;
 }
 
 export interface SingleEditOperation {
diff --git a/packages/plugin-ext/src/plugin/languages/completion.ts b/packages/plugin-ext/src/plugin/languages/completion.ts
index 212539c1e8067..b593472d1f8b4 100644
--- a/packages/plugin-ext/src/plugin/languages/completion.ts
+++ b/packages/plugin-ext/src/plugin/languages/completion.ts
@@ -16,7 +16,7 @@
 
 import { URI } from 'vscode-uri';
 import * as theia from '@theia/plugin';
-import { CompletionList, Range, SnippetString } from '../types-impl';
+import { CompletionItemTag, CompletionList, Range, SnippetString } from '../types-impl';
 import { DocumentsExtImpl } from '../documents';
 import * as Converter from '../type-converters';
 import { Position } from '../../common/plugin-api-rpc';
@@ -146,6 +146,10 @@ export class CompletionAdapter {
             };
         }
 
+        const tags = (!!item.tags?.length || item.deprecated === true)
+            ? [CompletionItemTag.Deprecated]
+            : undefined;
+
         return {
             id,
             parentId,
@@ -161,7 +165,8 @@ export class CompletionAdapter {
             range,
             additionalTextEdits: item.additionalTextEdits && item.additionalTextEdits.map(Converter.fromTextEdit),
             command: this.commands.converter.toSafeCommand(item.command, toDispose),
-            commitCharacters: item.commitCharacters
+            commitCharacters: item.commitCharacters,
+            tags
         };
     }
 
diff --git a/packages/plugin/src/theia.d.ts b/packages/plugin/src/theia.d.ts
index c98a4ad227002..149e1e599d460 100644
--- a/packages/plugin/src/theia.d.ts
+++ b/packages/plugin/src/theia.d.ts
@@ -6489,6 +6489,11 @@ declare module '@theia/plugin' {
          */
         textEdit?: TextEdit;
 
+        /**
+         * @deprecated Use `CompletionItem.tags` instead.
+         */
+        deprecated?: boolean;
+
         /**
          * Creates a new completion item.
          *