diff --git a/packages/compiler-cli/ngcc/src/packages/build_marker.ts b/packages/compiler-cli/ngcc/src/packages/build_marker.ts
index 4cc43207e3..554ccccc64 100644
--- a/packages/compiler-cli/ngcc/src/packages/build_marker.ts
+++ b/packages/compiler-cli/ngcc/src/packages/build_marker.ts
@@ -57,6 +57,17 @@ export function markAsProcessed(
     processed[prop] = NGCC_VERSION;
   }
 
+  const scripts = packageJson.scripts || (packageJson.scripts = {});
+  scripts.prepublishOnly__ivy_ngcc_bak =
+      scripts.prepublishOnly__ivy_ngcc_bak || scripts.prepublishOnly;
+
+  scripts.prepublishOnly = 'node --eval \"console.error(\'' +
+      'ERROR: Trying to publish a package that has been compiled by NGCC. This is not allowed.\\n' +
+      'Please delete and rebuild the package, without compiling with NGCC, before attempting to publish.\\n' +
+      'Note that NGCC may have been run by importing this package into another project that is being built with Ivy enabled.\\n' +
+      '\')\" ' +
+      '&& exit 1';
+
   // Just in case this package.json was synthesized due to a custom configuration
   // we will ensure that the path to the containing folder exists before we write the file.
   fs.ensureDir(dirname(packageJsonPath));
diff --git a/packages/compiler-cli/ngcc/src/packages/entry_point.ts b/packages/compiler-cli/ngcc/src/packages/entry_point.ts
index a173a59472..8884a16804 100644
--- a/packages/compiler-cli/ngcc/src/packages/entry_point.ts
+++ b/packages/compiler-cli/ngcc/src/packages/entry_point.ts
@@ -55,7 +55,8 @@ export interface PackageJsonFormatProperties {
  */
 export interface EntryPointPackageJson extends PackageJsonFormatProperties {
   name: string;
-  __processed_by_ivy_ngcc__?: {[key: string]: string};
+  scripts?: Record<string, string>;
+  __processed_by_ivy_ngcc__?: Record<string, string>;
 }
 
 export type EntryPointJsonProperty = Exclude<keyof PackageJsonFormatProperties, 'types'|'typings'>;
diff --git a/packages/compiler-cli/ngcc/test/packages/build_marker_spec.ts b/packages/compiler-cli/ngcc/test/packages/build_marker_spec.ts
index c288fad146..15dc9883e6 100644
--- a/packages/compiler-cli/ngcc/test/packages/build_marker_spec.ts
+++ b/packages/compiler-cli/ngcc/test/packages/build_marker_spec.ts
@@ -84,6 +84,7 @@ runInEachFileSystem(() => {
         const fs = getFileSystem();
         let pkg = JSON.parse(fs.readFile(COMMON_PACKAGE_PATH));
         expect(pkg.__processed_by_ivy_ngcc__).toBeUndefined();
+        expect(pkg.scripts).toBeUndefined();
 
         markAsProcessed(fs, pkg, COMMON_PACKAGE_PATH, ['fesm2015', 'fesm5']);
         pkg = JSON.parse(fs.readFile(COMMON_PACKAGE_PATH));
@@ -91,6 +92,7 @@ runInEachFileSystem(() => {
         expect(pkg.__processed_by_ivy_ngcc__.fesm5).toBe('0.0.0-PLACEHOLDER');
         expect(pkg.__processed_by_ivy_ngcc__.esm2015).toBeUndefined();
         expect(pkg.__processed_by_ivy_ngcc__.esm5).toBeUndefined();
+        expect(pkg.scripts.prepublishOnly).toBeDefined();
 
         markAsProcessed(fs, pkg, COMMON_PACKAGE_PATH, ['esm2015', 'esm5']);
         pkg = JSON.parse(fs.readFile(COMMON_PACKAGE_PATH));
@@ -98,6 +100,7 @@ runInEachFileSystem(() => {
         expect(pkg.__processed_by_ivy_ngcc__.fesm5).toBe('0.0.0-PLACEHOLDER');
         expect(pkg.__processed_by_ivy_ngcc__.esm2015).toBe('0.0.0-PLACEHOLDER');
         expect(pkg.__processed_by_ivy_ngcc__.esm5).toBe('0.0.0-PLACEHOLDER');
+        expect(pkg.scripts.prepublishOnly).toBeDefined();
       });
 
       it('should update the packageJson object in-place', () => {
@@ -105,18 +108,21 @@ runInEachFileSystem(() => {
         const fs = getFileSystem();
         const pkg = JSON.parse(fs.readFile(COMMON_PACKAGE_PATH));
         expect(pkg.__processed_by_ivy_ngcc__).toBeUndefined();
+        expect(pkg.scripts).toBeUndefined();
 
         markAsProcessed(fs, pkg, COMMON_PACKAGE_PATH, ['fesm2015', 'fesm5']);
         expect(pkg.__processed_by_ivy_ngcc__.fesm2015).toBe('0.0.0-PLACEHOLDER');
         expect(pkg.__processed_by_ivy_ngcc__.fesm5).toBe('0.0.0-PLACEHOLDER');
         expect(pkg.__processed_by_ivy_ngcc__.esm2015).toBeUndefined();
         expect(pkg.__processed_by_ivy_ngcc__.esm5).toBeUndefined();
+        expect(pkg.scripts.prepublishOnly).toBeDefined();
 
         markAsProcessed(fs, pkg, COMMON_PACKAGE_PATH, ['esm2015', 'esm5']);
         expect(pkg.__processed_by_ivy_ngcc__.fesm2015).toBe('0.0.0-PLACEHOLDER');
         expect(pkg.__processed_by_ivy_ngcc__.fesm5).toBe('0.0.0-PLACEHOLDER');
         expect(pkg.__processed_by_ivy_ngcc__.esm2015).toBe('0.0.0-PLACEHOLDER');
         expect(pkg.__processed_by_ivy_ngcc__.esm5).toBe('0.0.0-PLACEHOLDER');
+        expect(pkg.scripts.prepublishOnly).toBeDefined();
       });
 
       it('should one perform one write operation for all updated properties', () => {
@@ -128,6 +134,19 @@ runInEachFileSystem(() => {
         markAsProcessed(fs, pkg, COMMON_PACKAGE_PATH, ['fesm2015', 'fesm5', 'esm2015', 'esm5']);
         expect(writeFileSpy).toHaveBeenCalledTimes(1);
       });
+
+      it(`should keep backup of existing 'prepublishOnly' script`, () => {
+        const COMMON_PACKAGE_PATH = _('/node_modules/@angular/common/package.json');
+        const fs = getFileSystem();
+        const prepublishOnly = 'existing script';
+        let pkg = JSON.parse(fs.readFile(COMMON_PACKAGE_PATH));
+        pkg.scripts = {prepublishOnly};
+
+        markAsProcessed(fs, pkg, COMMON_PACKAGE_PATH, ['fesm2015']);
+        pkg = JSON.parse(fs.readFile(COMMON_PACKAGE_PATH));
+        expect(pkg.scripts.prepublishOnly).toContain('This is not allowed');
+        expect(pkg.scripts.prepublishOnly__ivy_ngcc_bak).toBe(prepublishOnly);
+      });
     });
 
     describe('hasBeenProcessed', () => {