diff --git a/packages/metro-cache-key/.npmignore b/packages/metro-cache-key/.npmignore
new file mode 100644
index 0000000000..a0d4570202
--- /dev/null
+++ b/packages/metro-cache-key/.npmignore
@@ -0,0 +1,5 @@
+**/__mocks__/**
+**/__tests__/**
+build
+src.real
+yarn.lock
diff --git a/packages/metro-symbolicate/.npmignore b/packages/metro-symbolicate/.npmignore
new file mode 100644
index 0000000000..a0d4570202
--- /dev/null
+++ b/packages/metro-symbolicate/.npmignore
@@ -0,0 +1,5 @@
+**/__mocks__/**
+**/__tests__/**
+build
+src.real
+yarn.lock
diff --git a/packages/metro-transform-worker/.npmignore b/packages/metro-transform-worker/.npmignore
new file mode 100644
index 0000000000..a0d4570202
--- /dev/null
+++ b/packages/metro-transform-worker/.npmignore
@@ -0,0 +1,5 @@
+**/__mocks__/**
+**/__tests__/**
+build
+src.real
+yarn.lock
diff --git a/scripts/__tests__/subpackages-test.js b/scripts/__tests__/subpackages-test.js
index 8c165fc15a..7c1c9dc89c 100644
--- a/scripts/__tests__/subpackages-test.js
+++ b/scripts/__tests__/subpackages-test.js
@@ -81,3 +81,20 @@ it('forces all packages to have a src/ folder', () => {
     );
   });
 });
+
+it('forces all packages to have an .npmignore with expected entries', () => {
+  checkAssertionInPackages(getPackages(), packagePath => {
+    const npmIgnorePath = path.join(packagePath, '.npmignore');
+    expect(fs.existsSync(npmIgnorePath)).toBe(true);
+    const lines = fs.readFileSync(npmIgnorePath, 'utf-8').split('\n');
+    expect(lines).toEqual(
+      expect.arrayContaining([
+        '**/__mocks__/**',
+        '**/__tests__/**',
+        'build',
+        'src.real',
+        'yarn.lock',
+      ]),
+    );
+  });
+});