diff --git a/packages/core/lib/iserror.d.ts b/packages/core/lib/iserror.d.ts
new file mode 100644
index 0000000000..b0c8ab398d
--- /dev/null
+++ b/packages/core/lib/iserror.d.ts
@@ -0,0 +1 @@
+export default function isError(maybeError: unknown): maybeError is Error
diff --git a/packages/plugin-window-unhandled-rejection/package.json b/packages/plugin-window-unhandled-rejection/package.json
index f0afa38985..8fba595d67 100644
--- a/packages/plugin-window-unhandled-rejection/package.json
+++ b/packages/plugin-window-unhandled-rejection/package.json
@@ -1,7 +1,15 @@
 {
   "name": "@bugsnag/plugin-window-unhandled-rejection",
   "version": "8.0.0",
-  "main": "unhandled-rejection.js",
+  "main": "dist/unhandled-rejection.js",
+  "types": "dist/types/unhandled-rejection.d.ts",
+  "exports": {
+    ".": {
+      "types": "./dist/types/unhandled-rejection.d.ts",
+      "default": "./dist/unhandled-rejection.js",
+      "import": "./dist/unhandled-rejection.mjs"
+    }
+  },
   "description": "@bugsnag/js plugin to report unhandled promise rejections in browsers",
   "homepage": "https://www.bugsnag.com/",
   "repository": {
@@ -21,5 +29,10 @@
   },
   "peerDependencies": {
     "@bugsnag/core": "^8.0.0"
+  },
+  "scripts": {
+    "build": "npm run build:npm",
+    "build:npm": "rollup --config rollup.config.npm.mjs",
+    "clean": "rm -rf dist/*"
   }
 }
diff --git a/packages/plugin-window-unhandled-rejection/rollup.config.npm.mjs b/packages/plugin-window-unhandled-rejection/rollup.config.npm.mjs
new file mode 100644
index 0000000000..6b32b19f98
--- /dev/null
+++ b/packages/plugin-window-unhandled-rejection/rollup.config.npm.mjs
@@ -0,0 +1,25 @@
+import createRollupConfig from '../../.rollup/index.mjs'
+
+export default createRollupConfig({
+    input: 'src/unhandled-rejection.ts',
+    output: [
+        {
+            dir: `dist`,
+            entryFileNames: '[name].js',
+            format: 'cjs',
+            preserveModules: true,
+            generatedCode: {
+              preset: 'es2015',
+            }
+        },
+        {
+            dir: `dist`,
+            entryFileNames: '[name].mjs',
+            format: 'esm',
+            preserveModules: true,
+            generatedCode: {
+                preset: 'es2015',
+            }
+        }
+    ]
+})
diff --git a/packages/plugin-window-unhandled-rejection/unhandled-rejection.js b/packages/plugin-window-unhandled-rejection/src/unhandled-rejection.ts
similarity index 73%
rename from packages/plugin-window-unhandled-rejection/unhandled-rejection.js
rename to packages/plugin-window-unhandled-rejection/src/unhandled-rejection.ts
index f766ab2707..85e0e287d3 100644
--- a/packages/plugin-window-unhandled-rejection/unhandled-rejection.js
+++ b/packages/plugin-window-unhandled-rejection/src/unhandled-rejection.ts
@@ -1,21 +1,28 @@
-const map = require('@bugsnag/core/lib/es-utils/map')
-const isError = require('@bugsnag/core/lib/iserror')
+import { Plugin, Stackframe } from '@bugsnag/core'
+import map from '@bugsnag/core/lib/es-utils/map'
+import isError from '@bugsnag/core/lib/iserror'
+
+type Listener = (evt: PromiseRejectionEvent) => void
+
+let _listener: Listener | null
 
-let _listener
 /*
  * Automatically notifies Bugsnag when window.onunhandledrejection is called
  */
-module.exports = (win = window) => {
-  const plugin = {
+export default (win = window): Plugin => {
+  const plugin: Plugin = {
     load: (client) => {
+      // @ts-expect-error _config is private API
       if (!client._config.autoDetectErrors || !client._config.enabledErrorTypes.unhandledRejections) return
-      const listener = evt => {
+      const listener = (evt: PromiseRejectionEvent) => {
         let error = evt.reason
         let isBluebird = false
 
         // accessing properties on evt.detail can throw errors (see #394)
         try {
+          // @ts-expect-error detail does not exist on type PromiseRejectionEvent
           if (evt.detail && evt.detail.reason) {
+            // @ts-expect-error detail does not exist on type PromiseRejectionEvent
             error = evt.detail.reason
             isBluebird = true
           }
@@ -25,6 +32,7 @@ module.exports = (win = window) => {
           severity: 'error',
           unhandled: true,
           severityReason: { type: 'unhandledPromiseRejection' }
+          // @ts-expect-error _logger is private API
         }, 'unhandledrejection handler', 1, client._logger)
 
         if (isBluebird) {
@@ -37,6 +45,7 @@ module.exports = (win = window) => {
               [Object.prototype.toString.call(event.originalError)]: {
                 name: event.originalError.name,
                 message: event.originalError.message,
+                // @ts-expect-error Property 'code' does not exist on type 'Error'
                 code: event.originalError.code
               }
             })
@@ -46,7 +55,9 @@ module.exports = (win = window) => {
       if ('addEventListener' in win) {
         win.addEventListener('unhandledrejection', listener)
       } else {
+        // @ts-expect-error onunhandledrejection does not exist on type never
         win.onunhandledrejection = (reason, promise) => {
+          // @ts-expect-error detail does not exist on type PromiseRejectionEvent
           listener({ detail: { reason, promise } })
         }
       }
@@ -54,13 +65,14 @@ module.exports = (win = window) => {
     }
   }
 
+  // @ts-expect-error cannot find name 'process'
   if (process.env.NODE_ENV !== 'production') {
     plugin.destroy = (win = window) => {
       if (_listener) {
         if ('addEventListener' in win) {
           win.removeEventListener('unhandledrejection', _listener)
         } else {
-          win.onunhandledrejection = null
+          (win as Window).onunhandledrejection = null
         }
       }
       _listener = null
@@ -88,7 +100,7 @@ module.exports = (win = window) => {
 //
 // Bluebird pads method names with spaces so trim that too…
 // https://github.com/petkaantonov/bluebird/blob/b7f21399816d02f979fe434585334ce901dcaf44/src/debuggability.js#L568-L571
-const fixBluebirdStacktrace = (error) => (frame) => {
+const fixBluebirdStacktrace = (error: PromiseRejectionEvent['reason']) => (frame: Stackframe) => {
   if (frame.file === error.toString()) return
   if (frame.method) {
     frame.method = frame.method.replace(/^\s+/, '')
diff --git a/packages/plugin-window-unhandled-rejection/test/unhandled-rejection.test.ts b/packages/plugin-window-unhandled-rejection/test/unhandled-rejection.test.ts
index 9b5b6da1c5..3e6c99b89f 100644
--- a/packages/plugin-window-unhandled-rejection/test/unhandled-rejection.test.ts
+++ b/packages/plugin-window-unhandled-rejection/test/unhandled-rejection.test.ts
@@ -1,5 +1,5 @@
 /* eslint-disable jest/no-commented-out-tests */
-import plugin from '../'
+import plugin from '../src/unhandled-rejection'
 
 import Client from '@bugsnag/core/client'
 
diff --git a/packages/plugin-window-unhandled-rejection/tsconfig.json b/packages/plugin-window-unhandled-rejection/tsconfig.json
new file mode 100644
index 0000000000..c76cdab7cd
--- /dev/null
+++ b/packages/plugin-window-unhandled-rejection/tsconfig.json
@@ -0,0 +1,8 @@
+{
+    "extends": "../../tsconfig.json",
+    "include": ["src/**/*.ts"],
+    "compilerOptions": {
+      "target": "ES2020"
+    }
+}
+  
\ No newline at end of file
diff --git a/tsconfig.json b/tsconfig.json
index 194cb11f2f..ba66910c52 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -81,7 +81,6 @@
     "packages/plugin-restify",
     "packages/node",
     "packages/plugin-client-ip",
-    "packages/plugin-window-unhandled-rejection",
     "packages/plugin-strip-query-string",
     "packages/plugin-strip-project-root",
     "packages/plugin-interaction-breadcrumbs",