diff --git a/.github/plugin/marketplace.json b/.github/plugin/marketplace.json
index 95313489..7057e598 100644
--- a/.github/plugin/marketplace.json
+++ b/.github/plugin/marketplace.json
@@ -248,6 +248,29 @@
       "description": "Comprehensive collection for building declarative agents with Model Context Protocol integration for Microsoft 365 Copilot",
       "version": "1.0.0"
     },
+    {
+      "name": "modernize-dotnet",
+      "description": "AI-powered .NET modernization and upgrade assistant. Helps upgrade .NET Framework and .NET applications to the latest versions of .NET.",
+      "version": "1.0.979-preview1",
+      "author": {
+        "name": "Microsoft",
+        "url": "https://www.microsoft.com"
+      },
+      "homepage": "https://github.com/dotnet/modernize-dotnet",
+      "keywords": [
+        "modernization",
+        "upgrade",
+        "migration",
+        "dotnet"
+      ],
+      "license": "MIT",
+      "repository": "https://github.com/dotnet/modernize-dotnet",
+      "source": {
+        "source": "github",
+        "repo": "dotnet/modernize-dotnet",
+        "path": "plugins/modernize-dotnet"
+      }
+    },
     {
       "name": "napkin",
       "source": "napkin",
diff --git a/plugins/external.json b/plugins/external.json
index 4c730be7..e4b4c0f5 100644
--- a/plugins/external.json
+++ b/plugins/external.json
@@ -87,5 +87,23 @@
     "source": "github",
     "repo": "microsoft/skills-for-copilot-studio"
     }
+  },
+  {
+    "name": "modernize-dotnet",
+    "description": "AI-powered .NET modernization and upgrade assistant. Helps upgrade .NET Framework and .NET applications to the latest versions of .NET.",
+    "version": "1.0.979-preview1",
+    "author": {
+      "name": "Microsoft",
+      "url": "https://www.microsoft.com"
+    },
+    "homepage": "https://github.com/dotnet/modernize-dotnet",
+    "keywords": ["modernization", "upgrade", "migration", "dotnet"],
+    "license": "MIT",
+    "repository": "https://github.com/dotnet/modernize-dotnet",
+    "source": {
+      "source": "github",
+      "repo": "dotnet/modernize-dotnet",
+      "path": "plugins/modernize-dotnet"
+    }
   }
 ]