diff --git a/azure-pipelines/1esmain.yml b/azure-pipelines/1esmain.yml
index f6bfd1e070..e5d88f4bd6 100644
--- a/azure-pipelines/1esmain.yml
+++ b/azure-pipelines/1esmain.yml
@@ -19,6 +19,13 @@ parameters:
   - name: npmFeed
     type: string
     default: DevDiv/azcode
+  # Azure Artifacts feed for a private NuGet mirror used during the signing step
+  # (the SignExtension.signproj references Microsoft.VisualStudioEng.MicroBuild.Core).
+  # Configure this feed in Azure DevOps to upstream api.nuget.org/v3/index.json
+  # so that builds don't reach out to public nuget.org.
+  - name: nugetFeed
+    type: string
+    default: DevDiv/azcode
   - name: additionalPostPackageSteps
     type: stepList
     default: []
@@ -74,6 +81,7 @@ extends:
           bamiVariablesGroupName: ${{ parameters.bamiVariablesGroupName }}
           additionalSetupSteps: ${{ parameters.additionalSetupSteps }}
           npmFeed: ${{ parameters.npmFeed }}
+          nugetFeed: ${{ parameters.nugetFeed }}
           additionalPostPackageSteps: ${{ parameters.additionalPostPackageSteps }}
           enableSigning: ${{ parameters.enableSigning }}
           vsixFileNames: ${{ parameters.vsixFileNames }}
diff --git a/azure-pipelines/1esstages.yml b/azure-pipelines/1esstages.yml
index 164d15034e..4a72febf9b 100644
--- a/azure-pipelines/1esstages.yml
+++ b/azure-pipelines/1esstages.yml
@@ -20,6 +20,10 @@ parameters:
   - name: npmFeed
     type: string
     default: DevDiv/azcode
+  # Azure Artifacts feed for a private NuGet mirror (used by the signing step)
+  - name: nugetFeed
+    type: string
+    default: DevDiv/azcode
   - name: additionalPostPackageSteps
     type: stepList
     default: []
@@ -65,6 +69,7 @@ stages:
                   vsixFileNames: ${{ parameters.vsixFileNames }}
                   workingDirectory: ${{ job.working_directory }}
                   npmFeed: ${{ parameters.npmFeed }}
+                  nugetFeed: ${{ parameters.nugetFeed }}
 
               - template: ./templates/stage-artifacts.yml
               - template: ./templates/test.yml
diff --git a/azure-pipelines/README.md b/azure-pipelines/README.md
index 73777d516d..7fdc3a9392 100644
--- a/azure-pipelines/README.md
+++ b/azure-pipelines/README.md
@@ -120,6 +120,18 @@ extends:
 </Project>
 ```
 
+> **NuGet feed prerequisite for signing:** The signing step runs `dotnet` against
+> `SignExtension.signproj`, which has a `PackageReference` on
+> `Microsoft.VisualStudioEng.MicroBuild.Core`. To avoid the build reaching out
+> to public `nuget.org`, the templates restore that package from the Azure
+> Artifacts feed identified by the `nugetFeed` parameter (defaults to
+> `DevDiv/azcode`). That feed must be configured in Azure DevOps to have
+> `api.nuget.org/v3/index.json` as an upstream source. If your feed does not
+> mirror NuGet, either (a) add a NuGet upstream to the feed, or (b) override
+> the `nugetFeed` parameter when extending the template (set it to `''` to
+> fall back to the default NuGet sources, or to a different `Project/Feed`
+> name).
+
 ### Extension release pipeline
 
 This pipeline downloads and releases signed VSIX artifacts from the specified build pipeline.
diff --git a/azure-pipelines/templates/sign.yml b/azure-pipelines/templates/sign.yml
index 41838bc019..fccfc98e4f 100644
--- a/azure-pipelines/templates/sign.yml
+++ b/azure-pipelines/templates/sign.yml
@@ -11,6 +11,17 @@ parameters:
   - name: npmFeed
     type: string
     default: DevDiv/azcode
+  # Azure Artifacts feed for a private NuGet mirror used when restoring the
+  # SignExtension.signproj project. This avoids reaching out to nuget.org from
+  # the signing step. Set to '' to fall back to the default NuGet sources.
+  - name: nugetFeed
+    type: string
+    default: DevDiv/azcode
+  # Internal NuGet v3 index used to force restore to a single source via
+  # command-line arguments without requiring a repo-local NuGet.config.
+  - name: nugetFeedUrl
+    type: string
+    default: https://devdiv.pkgs.visualstudio.com/DevDiv/_packaging/azcode/nuget/v3/index.json
 
 steps:
   # Check if the SignExtension.signproj file exists and set a variable using PowerShell
@@ -56,6 +67,23 @@ steps:
         customRegistry: useFeed
         customFeed: ${{ parameters.npmFeed }}
 
+  # Restore the signing project's NuGet packages (e.g. Microsoft.VisualStudioEng.MicroBuild.Core)
+  # from the internal Azure Artifacts feed rather than nuget.org. The build steps below pass
+  # --no-restore so they don't trigger an implicit restore against the public feed.
+  - task: DotNetCoreCLI@2
+    condition: and(succeeded(), eq(variables['signprojExists'], True))
+    displayName: "\U0001F449 Restore signing project from internal NuGet feed"
+    inputs:
+      command: "restore"
+      projects: $(signprojPath)
+      ${{ if ne(parameters.nugetFeed, '') }}:
+        feedsToUse: "select"
+        vstsFeed: ${{ parameters.nugetFeed }}
+        includeNuGetOrg: false
+        restoreArguments: >-
+          --source ${{ parameters.nugetFeedUrl }}
+          /p:NuGetAudit=false
+
   # Sign single vsix file if vsixFileNames are not provided
   - ${{ if eq(join('', parameters.vsixFileNames), '') }}:
       - script: vsce generate-manifest -i $(package.name)-$(package.version).vsix -o $(Build.SourcesDirectory)/${{ parameters.workingDirectory }}/extension.manifest
@@ -70,7 +98,7 @@ steps:
         inputs:
           command: "build"
           projects: $(signprojPath)
-          arguments: "/p:ProjectDir=$(Build.SourcesDirectory)/${{ parameters.workingDirectory }}/.azure-pipelines/"
+          arguments: "/p:ProjectDir=$(Build.SourcesDirectory)/${{ parameters.workingDirectory }}/.azure-pipelines/ --no-restore"
         env:
           SYSTEM_ACCESSTOKEN: $(System.AccessToken)
 
@@ -104,7 +132,7 @@ steps:
             inputs:
               command: "build"
               projects: $(signprojPath)
-              arguments: "/p:ProjectDir=$(Build.SourcesDirectory)/${{ parameters.workingDirectory }}/.azure-pipelines/"
+              arguments: "/p:ProjectDir=$(Build.SourcesDirectory)/${{ parameters.workingDirectory }}/.azure-pipelines/ --no-restore"
             env:
               SYSTEM_ACCESSTOKEN: $(System.AccessToken)