diff --git a/README.md b/README.md
index 3bb9456..ea7770d 100644
--- a/README.md
+++ b/README.md
@@ -24,5 +24,5 @@ Communication framework for browser extensions, with wings!
 
 ## Supports
 
-* **Runtime contexts:** window (injected script), popup, devtools, content script, background, options, sidepanel (_planned_)
+* **Runtime contexts:** window (injected script), popup, sidepanel, devtools, content script, background, options
 * **Browsers:** Chrome, Firefox, Safari, Opera, Edge + others supported by [webextension-polyfill](https://github.com/mozilla/webextension-polyfill)
diff --git a/packages/rpc/src/types.ts b/packages/rpc/src/types.ts
index 21e9030..4933b2d 100644
--- a/packages/rpc/src/types.ts
+++ b/packages/rpc/src/types.ts
@@ -4,6 +4,7 @@ export type RuntimeContext =
   | 'devtools'
   | 'background'
   | 'popup'
+  | 'sidepanel'
   | 'options'
   | 'content-script'
   | 'window';
diff --git a/packages/transport/README.md b/packages/transport/README.md
index c6542a4..ddca66d 100644
--- a/packages/transport/README.md
+++ b/packages/transport/README.md
@@ -19,7 +19,7 @@ This library provides two communication patterns:
 
 ## Supports
 
-* **Runtime contexts:** window (injected script), popup, devtools, content script, background, options, sidepanel (_planned_)
+* **Runtime contexts:** window (injected script), popup, sidepanel, devtools, content script, background, options
 * **Browsers:** Chrome, Firefox, Safari, Opera, Edge + others supported by [webextension-polyfill](https://github.com/mozilla/webextension-polyfill)
 
 ## Comparison to other libraries
@@ -88,6 +88,7 @@ eventBus.emitBroadcastEvent(
  - `@webext-pegasus/transport/devtools`
  - `@webext-pegasus/transport/options`
  - `@webext-pegasus/transport/popup`
+ - `@webext-pegasus/transport/sidepanel`
  - `@webext-pegasus/transport/window` (for injected scripts)
 
 
@@ -125,7 +126,7 @@ initPegasusTransport();
 
 ## Security risks while communicating with injected script
 
-The following note only applies if and only if, you will be sending/receiving messages to/from `window` contexts. There's no security concern if you will be only working with `content-script`, `background`, `popup`, `options`, or `devtools` scope, which is the default setting.
+The following note only applies if and only if, you will be sending/receiving messages to/from `window` contexts. There's no security concern if you will be only working with `content-script`, `background`, `popup`, `sidepanel`, `options`, or `devtools` scope, which is the default setting.
 
 `window` context(s) in tab `A` get unlocked the moment you call `initPegasusTransport({allowWindowMessagingForNamespace: 'TEST'})` in your extension's content script AND `initPegasusTransport({namespace: 'TEST'})` in your injected script.
 
@@ -142,7 +143,7 @@ import { onMessage } from '@webext-pegasus/transport/background';
 
 onMessage("getUserBrowsingHistory", (message) => {
   const { data, sender } = message;
-  // Respond only if request is from 'devtools', 'content-script', 'popup', 'options', or 'background' endpoint
+  // Respond only if request is from 'devtools', 'content-script', 'popup', 'sidepanel', 'options', or 'background' endpoint
 });
 ```
 
diff --git a/packages/transport/package.json b/packages/transport/package.json
index 0d4d30f..a415318 100644
--- a/packages/transport/package.json
+++ b/packages/transport/package.json
@@ -17,7 +17,7 @@
   ],
   "scripts": {
     "test": "echo \"Error: no test specified\" && exit 1",
-    "tsup-build": "tsup index.ts background.ts content-script.ts devtools.ts popup.ts window.ts options.ts --format cjs,esm --dts",
+    "tsup-build": "tsup index.ts background.ts content-script.ts devtools.ts popup.ts sidepanel.ts window.ts options.ts --format cjs,esm --dts",
     "build": "npm run tsup-build --dts-resolve",
     "prepublishOnly": "npm run build"
   },
@@ -47,6 +47,10 @@
       "import": "./dist/popup.js",
       "require": "./dist/popup.cjs"
     },
+    "./sidepanel": {
+      "import": "./dist/sidepanel.js",
+      "require": "./dist/sidepanel.cjs"
+    },
     "./window": {
       "import": "./dist/window.js",
       "require": "./dist/window.cjs"
@@ -72,6 +76,9 @@
       "popup": [
         "dist/popup.d.ts"
       ],
+      "sidepanel": [
+        "dist/sidepanel.d.ts"
+      ],
       "window": [
         "dist/window.d.ts"
       ]
diff --git a/packages/transport/sidepanel.ts b/packages/transport/sidepanel.ts
new file mode 100644
index 0000000..1cc1ccd
--- /dev/null
+++ b/packages/transport/sidepanel.ts
@@ -0,0 +1,33 @@
+import browser from 'webextension-polyfill';
+
+import {createBroadcastEventRuntime} from './src/BroadcastEventRuntime';
+import {createMessageRuntime} from './src/MessageRuntime';
+import {createPersistentPort} from './src/PersistentPort';
+import {initTransportAPI} from './src/TransportAPI';
+import {internalPacketTypeRouter} from './src/utils/internalPacketTypeRouter';
+
+export function initPegasusTransport(): void {
+  const port = createPersistentPort('sidepanel');
+  const messageRuntime = createMessageRuntime('sidepanel', async (message) =>
+    port.postMessage(message),
+  );
+
+  port.onMessage((packet) =>
+    internalPacketTypeRouter(packet, {eventRuntime, messageRuntime}),
+  );
+
+  const eventRuntime = createBroadcastEventRuntime(
+    'sidepanel',
+    async (event) => {
+      port.postMessage(event);
+    },
+  );
+
+  initTransportAPI({
+    browser: browser,
+    emitBroadcastEvent: eventRuntime.emitBroadcastEvent,
+    onBroadcastEvent: eventRuntime.onBroadcastEvent,
+    onMessage: messageRuntime.onMessage,
+    sendMessage: messageRuntime.sendMessage,
+  });
+}
diff --git a/packages/transport/src/isInternalEndpoint.ts b/packages/transport/src/isInternalEndpoint.ts
index ea09ecd..82ffea0 100644
--- a/packages/transport/src/isInternalEndpoint.ts
+++ b/packages/transport/src/isInternalEndpoint.ts
@@ -6,6 +6,7 @@ const internalEndpoints: RuntimeContext[] = [
   'content-script',
   'options',
   'popup',
+  'sidepanel',
 ];
 
 export const isInternalEndpoint = ({context: ctx}: Endpoint): boolean =>
diff --git a/packages/transport/src/types.ts b/packages/transport/src/types.ts
index 3553b90..168bdc9 100644
--- a/packages/transport/src/types.ts
+++ b/packages/transport/src/types.ts
@@ -10,6 +10,7 @@ export type RuntimeContext =
   | 'devtools'
   | 'background'
   | 'popup'
+  | 'sidepanel'
   | 'options'
   | 'content-script'
   | 'window';
diff --git a/packages/transport/src/utils/endpoint-utils.ts b/packages/transport/src/utils/endpoint-utils.ts
index add9bc8..2e32f7a 100644
--- a/packages/transport/src/utils/endpoint-utils.ts
+++ b/packages/transport/src/utils/endpoint-utils.ts
@@ -1,7 +1,7 @@
 import type {Endpoint, RuntimeContext} from '../types';
 
 const ENDPOINT_RE =
-  /^((?:background$)|devtools|popup|options|content-script|window)(?:@(\d+)(?:\.(\d+))?)?$/;
+  /^((?:background$)|devtools|popup|sidepanel|options|content-script|window)(?:@(\d+)(?:\.(\d+))?)?$/;
 
 export const deserializeEndpoint = (endpoint: string): Endpoint => {
   const [, context, tabId, frameId] = endpoint.match(ENDPOINT_RE) || [];
@@ -18,7 +18,7 @@ export const serializeEndpoint = ({
   tabId,
   frameId,
 }: Endpoint): string => {
-  if (['background', 'popup', 'options'].includes(context)) {
+  if (['background', 'popup', 'sidepanel', 'options'].includes(context)) {
     return context;
   }