diff --git a/goldens/public-api/angular/build/index.api.md b/goldens/public-api/angular/build/index.api.md
index d09f6bf40a6a..9e35cbe6b158 100644
--- a/goldens/public-api/angular/build/index.api.md
+++ b/goldens/public-api/angular/build/index.api.md
@@ -149,6 +149,9 @@ export function executeDevServerBuilder(options: DevServerBuilderOptions, contex
 // @public
 export function executeExtractI18nBuilder(options: ExtractI18nBuilderOptions, context: BuilderContext, extensions?: ApplicationBuilderExtensions): Promise<BuilderOutput>;
 
+// @public
+export function executeNgPackagrBuilder(options: NgPackagrBuilderOptions, context: BuilderContext): AsyncIterableIterator<BuilderOutput>;
+
 // @public
 export interface ExtractI18nBuilderOptions {
     buildTarget?: string;
@@ -158,6 +161,14 @@ export interface ExtractI18nBuilderOptions {
     progress?: boolean;
 }
 
+// @public
+export interface NgPackagrBuilderOptions {
+    poll?: number;
+    project: string;
+    tsConfig?: string;
+    watch?: boolean;
+}
+
 // (No @packageDocumentation comment for this package)
 
 ```
diff --git a/packages/angular/build/BUILD.bazel b/packages/angular/build/BUILD.bazel
index 91868fb61cfd..ba11626610e7 100644
--- a/packages/angular/build/BUILD.bazel
+++ b/packages/angular/build/BUILD.bazel
@@ -23,6 +23,11 @@ ts_json_schema(
     src = "src/builders/extract-i18n/schema.json",
 )
 
+ts_json_schema(
+    name = "ng_packagr_schema",
+    src = "src/builders/ng-packagr/schema.json",
+)
+
 ts_project(
     name = "build",
     srcs = glob(
@@ -40,6 +45,7 @@ ts_project(
         "//packages/angular/build:src/builders/application/schema.ts",
         "//packages/angular/build:src/builders/dev-server/schema.ts",
         "//packages/angular/build:src/builders/extract-i18n/schema.ts",
+        "//packages/angular/build:src/builders/ng-packagr/schema.ts",
     ],
     data = glob(
         include = [
@@ -90,6 +96,7 @@ ts_project(
         "//:root_modules/lmdb",
         "//:root_modules/magic-string",
         "//:root_modules/mrmime",
+        "//:root_modules/ng-packagr",
         "//:root_modules/parse5-html-rewriting-stream",
         "//:root_modules/picomatch",
         "//:root_modules/piscina",
@@ -186,6 +193,7 @@ ts_project(
         "//:root_modules/@angular/platform-browser",
         "//:root_modules/@angular/platform-browser-dynamic",
         "//:root_modules/@angular/router",
+        "//:root_modules/ng-packagr",
         "//:root_modules/rxjs",
         "//:root_modules/tslib",
         "//:root_modules/typescript",
diff --git a/packages/angular/build/builders.json b/packages/angular/build/builders.json
index b0174fc3fee9..ef98f535c16c 100644
--- a/packages/angular/build/builders.json
+++ b/packages/angular/build/builders.json
@@ -14,6 +14,11 @@
       "implementation": "./src/builders/extract-i18n/index",
       "schema": "./src/builders/extract-i18n/schema.json",
       "description": "Extract i18n messages from an application."
+    },
+    "ng-packagr": {
+      "implementation": "./src/builders/ng-packagr/index",
+      "schema": "./src/builders/ng-packagr/schema.json",
+      "description": "Build a library with ng-packagr."
     }
   }
 }
diff --git a/packages/angular/build/package.json b/packages/angular/build/package.json
index 8b0b6a950849..9f0b998a476f 100644
--- a/packages/angular/build/package.json
+++ b/packages/angular/build/package.json
@@ -55,6 +55,7 @@
     "@angular/service-worker": "^19.0.0 || ^19.1.0-next.0",
     "@angular/ssr": "^0.0.0-PLACEHOLDER",
     "less": "^4.2.0",
+    "ng-packagr": "^19.0.0 || ^19.1.0-next.0",
     "postcss": "^8.4.0",
     "tailwindcss": "^2.0.0 || ^3.0.0",
     "typescript": ">=5.5 <5.8"
@@ -75,6 +76,9 @@
     "less": {
       "optional": true
     },
+    "ng-packagr": {
+      "optional": true
+    },
     "postcss": {
       "optional": true
     },
diff --git a/packages/angular/build/src/builders/ng-packagr/builder.ts b/packages/angular/build/src/builders/ng-packagr/builder.ts
new file mode 100644
index 000000000000..f2dc60ebf30c
--- /dev/null
+++ b/packages/angular/build/src/builders/ng-packagr/builder.ts
@@ -0,0 +1,86 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.dev/license
+ */
+
+import type { BuilderContext, BuilderOutput } from '@angular-devkit/architect';
+import type { NgPackagrOptions } from 'ng-packagr';
+import { join, resolve } from 'node:path';
+import { assertIsError } from '../../utils/error';
+import { normalizeCacheOptions } from '../../utils/normalize-cache';
+import { purgeStaleBuildCache } from '../../utils/purge-cache';
+import type { Schema as NgPackagrBuilderOptions } from './schema';
+
+/**
+ * A Builder that executes the `ng-packagr` tool to build an Angular library.
+ *
+ * @param options The builder options as defined by the JSON schema.
+ * @param context A BuilderContext instance.
+ * @returns A BuilderOutput object.
+ *
+ * @experimental Direct usage of this function is considered experimental.
+ */
+export async function* execute(
+  options: NgPackagrBuilderOptions,
+  context: BuilderContext,
+): AsyncIterableIterator<BuilderOutput> {
+  // Purge old build disk cache.
+  await purgeStaleBuildCache(context);
+
+  const root = context.workspaceRoot;
+  let packager;
+  try {
+    packager = (await import('ng-packagr')).ngPackagr();
+  } catch (error) {
+    assertIsError(error);
+    if (error.code === 'MODULE_NOT_FOUND') {
+      return {
+        success: false,
+        error:
+          'The "ng-packagr" package was not found. To correct this error, ensure this package is installed in the project.',
+      };
+    }
+
+    throw error;
+  }
+
+  packager.forProject(resolve(root, options.project));
+
+  if (options.tsConfig) {
+    packager.withTsConfig(resolve(root, options.tsConfig));
+  }
+
+  const projectName = context.target?.project;
+  if (!projectName) {
+    throw new Error('The builder requires a target.');
+  }
+
+  const metadata = await context.getProjectMetadata(projectName);
+  const { enabled: cacheEnabled, path: cacheDirectory } = normalizeCacheOptions(
+    metadata,
+    context.workspaceRoot,
+  );
+
+  const ngPackagrOptions: NgPackagrOptions = {
+    cacheEnabled,
+    poll: options.poll,
+    cacheDirectory: join(cacheDirectory, 'ng-packagr'),
+  };
+
+  try {
+    if (options.watch) {
+      await packager.watch(ngPackagrOptions).toPromise();
+    } else {
+      await packager.build(ngPackagrOptions);
+    }
+
+    yield { success: true };
+  } catch (error) {
+    assertIsError(error);
+
+    yield { success: false, error: error.message };
+  }
+}
diff --git a/packages/angular/build/src/builders/ng-packagr/index.ts b/packages/angular/build/src/builders/ng-packagr/index.ts
new file mode 100644
index 000000000000..df32d691aa43
--- /dev/null
+++ b/packages/angular/build/src/builders/ng-packagr/index.ts
@@ -0,0 +1,14 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.dev/license
+ */
+
+import { createBuilder } from '@angular-devkit/architect';
+import { execute } from './builder';
+import type { Schema as NgPackagrBuilderOptions } from './schema';
+
+export { type NgPackagrBuilderOptions, execute };
+export default createBuilder<NgPackagrBuilderOptions>(execute);
diff --git a/packages/angular/build/src/builders/ng-packagr/schema.json b/packages/angular/build/src/builders/ng-packagr/schema.json
new file mode 100644
index 000000000000..da76255f092a
--- /dev/null
+++ b/packages/angular/build/src/builders/ng-packagr/schema.json
@@ -0,0 +1,27 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema",
+  "title": "ng-packagr Target",
+  "description": "ng-packagr target options for Build Architect. Use to build library projects.",
+  "type": "object",
+  "properties": {
+    "project": {
+      "type": "string",
+      "description": "The file path for the ng-packagr configuration file, relative to the current workspace."
+    },
+    "tsConfig": {
+      "type": "string",
+      "description": "The full path for the TypeScript configuration file, relative to the current workspace."
+    },
+    "watch": {
+      "type": "boolean",
+      "description": "Run build when files change.",
+      "default": false
+    },
+    "poll": {
+      "type": "number",
+      "description": "Enable and define the file watching poll time period in milliseconds."
+    }
+  },
+  "additionalProperties": false,
+  "required": ["project"]
+}
diff --git a/packages/angular/build/src/index.ts b/packages/angular/build/src/index.ts
index 64c5fc2f3b32..a27e1f5ae9d2 100644
--- a/packages/angular/build/src/index.ts
+++ b/packages/angular/build/src/index.ts
@@ -21,3 +21,8 @@ export {
   execute as executeExtractI18nBuilder,
   type ExtractI18nBuilderOptions,
 } from './builders/extract-i18n';
+
+export {
+  execute as executeNgPackagrBuilder,
+  type NgPackagrBuilderOptions,
+} from './builders/ng-packagr';
diff --git a/packages/angular/cli/BUILD.bazel b/packages/angular/cli/BUILD.bazel
index 15cf4e64008c..abee3d62b711 100644
--- a/packages/angular/cli/BUILD.bazel
+++ b/packages/angular/cli/BUILD.bazel
@@ -78,6 +78,7 @@ CLI_SCHEMA_DATA = [
     "//packages/angular/build:src/builders/application/schema.json",
     "//packages/angular/build:src/builders/dev-server/schema.json",
     "//packages/angular/build:src/builders/extract-i18n/schema.json",
+    "//packages/angular/build:src/builders/ng-packagr/schema.json",
     "//packages/angular_devkit/build_angular:src/builders/app-shell/schema.json",
     "//packages/angular_devkit/build_angular:src/builders/browser/schema.json",
     "//packages/angular_devkit/build_angular:src/builders/browser-esbuild/schema.json",
diff --git a/packages/angular/cli/lib/config/workspace-schema.json b/packages/angular/cli/lib/config/workspace-schema.json
index 402ad662cf09..edffabf285ef 100644
--- a/packages/angular/cli/lib/config/workspace-schema.json
+++ b/packages/angular/cli/lib/config/workspace-schema.json
@@ -407,6 +407,7 @@
                       "@angular/build:application",
                       "@angular/build:dev-server",
                       "@angular/build:extract-i18n",
+                      "@angular/build:ng-packagr",
                       "@angular-devkit/build-angular:application",
                       "@angular-devkit/build-angular:app-shell",
                       "@angular-devkit/build-angular:browser",
@@ -792,6 +793,28 @@
                   }
                 }
               }
+            },
+            {
+              "type": "object",
+              "additionalProperties": false,
+              "properties": {
+                "builder": {
+                  "const": "@angular/build:ng-packagr"
+                },
+                "defaultConfiguration": {
+                  "type": "string",
+                  "description": "A default named configuration to use when a target configuration is not provided."
+                },
+                "options": {
+                  "$ref": "../../../../angular/build/src/builders/ng-packagr/schema.json"
+                },
+                "configurations": {
+                  "type": "object",
+                  "additionalProperties": {
+                    "$ref": "../../../../angular/build/src/builders/ng-packagr/schema.json"
+                  }
+                }
+              }
             }
           ]
         }