diff --git a/packages/tree-select/package.json b/packages/tree-select/package.json
index 3a435ee99cc3c..8cdd1afcac4b1 100644
--- a/packages/tree-select/package.json
+++ b/packages/tree-select/package.json
@@ -11,7 +11,7 @@
 	"license": "GPL-2.0-or-later",
 	"main": "dist/cjs/index.js",
 	"module": "dist/esm/index.js",
-	"calypso:src": "src/index.js",
+	"calypso:src": "src/index.ts",
 	"sideEffects": false,
 	"repository": {
 		"type": "git",
@@ -28,9 +28,14 @@
 		"dist",
 		"src"
 	],
+	"types": "dist/types",
 	"scripts": {
-		"clean": "npx rimraf dist",
-		"build": "transpile",
-		"prepack": "yarn run clean && yarn run build"
+		"clean": "tsc --build ./tsconfig.json ./tsconfig-cjs.json --clean",
+		"build": "tsc --build ./tsconfig.json ./tsconfig-cjs.json",
+		"prepack": "yarn run clean && yarn run build",
+		"watch": "tsc --build ./tsconfig.json --watch"
+	},
+	"dependencies": {
+		"tslib": "^1.10.0"
 	}
 }
diff --git a/packages/tree-select/src/index.js b/packages/tree-select/src/index.ts
similarity index 50%
rename from packages/tree-select/src/index.js
rename to packages/tree-select/src/index.ts
index cf4c864471348..7c468d0712cb7 100644
--- a/packages/tree-select/src/index.js
+++ b/packages/tree-select/src/index.ts
@@ -1,25 +1,56 @@
-const defaultGetCacheKey = ( ...args ) => args.join();
+declare const process: {
+	env: {
+		NODE_ENV: unknown;
+	};
+};
+
+interface GenerateCacheKey< A extends unknown[] > {
+	( ...args: A ): string;
+}
+
+const defaultGetCacheKey: GenerateCacheKey< unknown[] > = ( ...args: unknown[] ): string =>
+	args.join();
 
-const isFunction = ( fn ) => {
-	return fn && typeof fn === 'function';
+const isFunction = ( fn: unknown ): fn is ( ...args: unknown[] ) => unknown => {
+	return !! fn && typeof fn === 'function';
 };
 
-const isObject = ( o ) => {
-	return o && typeof o === 'object';
+const isObject = ( o: unknown ): o is Record< string, unknown > => {
+	return !! o && typeof o === 'object';
 };
 
+type WeakMapKey = object; // eslint-disable-line @typescript-eslint/ban-types
+
+interface Options< A extends unknown[] > {
+	/** Custom way to compute the cache key from the `args` list */
+	getCacheKey?: GenerateCacheKey< A >;
+}
+
+interface CachedSelector< S, A extends unknown[], R = unknown > {
+	( state: S, ...args: A ): R;
+	clearCache: () => void;
+}
+
 /**
  * Returns a selector that caches values.
  *
- * @param  {Function} getDependents A Function describing the dependent(s) of the selector.
- *                                    Must return an array which gets passed as the first arg to the selector
- * @param  {Function} selector      A standard selector for calculating cached result
- * @param  {object}   options       Options bag with additional arguments
- * @param  {Function} options.getCacheKey
- *                                  Custom way to compute the cache key from the `args` list
- * @returns {Function}               Cached selector
+ * @param getDependents A Function describing the dependent(s) of the selector.
+ *                      Must return an array which gets passed as the first arg to the selector.
+ * @param selector      A standard selector for calculating cached result.
+ * @param options       Options bag with additional arguments.
+ *
+ * @returns Cached selector
  */
-export default function treeSelect( getDependents, selector, options = {} ) {
+export default function treeSelect<
+	State = unknown,
+	Args extends unknown[] = unknown[],
+	Deps extends WeakMapKey[] = any[], // eslint-disable-line @typescript-eslint/no-explicit-any
+	Result = unknown
+>(
+	getDependents: ( state: State, ...args: Args ) => Deps,
+	selector: ( deps: Deps, ...args: Args ) => Result,
+	options: Options< Args > = {}
+): CachedSelector< State, Args, Result > {
 	if ( process.env.NODE_ENV !== 'production' ) {
 		if ( ! isFunction( getDependents ) || ! isFunction( selector ) ) {
 			throw new TypeError(
@@ -32,7 +63,10 @@ export default function treeSelect( getDependents, selector, options = {} ) {
 
 	const { getCacheKey = defaultGetCacheKey } = options;
 
-	const cachedSelector = function ( state, ...args ) {
+	const cachedSelector: CachedSelector< State, Args, Result > = function (
+		state: State,
+		...args: Args
+	) {
 		const dependents = getDependents( state, ...args );
 
 		if ( process.env.NODE_ENV !== 'production' ) {
@@ -44,11 +78,11 @@ export default function treeSelect( getDependents, selector, options = {} ) {
 		// create a dependency tree for caching selector results.
 		// this is beneficial over standard memoization techniques so that we can
 		// garbage collect any values that are based on outdated dependents
-		const leafCache = dependents.reduce( insertDependentKey, cache );
+		const leafCache: Map< string, Result > = dependents.reduce( insertDependentKey, cache );
 
 		const key = getCacheKey( ...args );
 		if ( leafCache.has( key ) ) {
-			return leafCache.get( key );
+			return leafCache.get( key ) as Result;
 		}
 
 		const value = selector( dependents, ...args );
@@ -76,7 +110,8 @@ const NULLISH_KEY = {};
  * Note: Inserts WeakMaps except for the last map which will be a regular Map.
  * The last map is a regular one because the the key for the last map is the string results of args.join().
  */
-function insertDependentKey( map, key, currentIndex, arr ) {
+function insertDependentKey( map: any, key: unknown, currentIndex: number, arr: unknown[] ) {
+	// eslint-disable-line @typescript-eslint/no-explicit-any
 	if ( key != null && Object( key ) !== key ) {
 		throw new TypeError( 'key must be an object, `null`, or `undefined`' );
 	}
diff --git a/packages/tree-select/tsconfig-cjs.json b/packages/tree-select/tsconfig-cjs.json
new file mode 100644
index 0000000000000..bd64442da990d
--- /dev/null
+++ b/packages/tree-select/tsconfig-cjs.json
@@ -0,0 +1,12 @@
+{
+	"extends": "./tsconfig",
+	"compilerOptions": {
+		"module": "commonjs",
+		"declaration": false,
+		"declarationMap": false,
+		"declarationDir": null,
+		"outDir": "dist/cjs",
+		"composite": false,
+		"incremental": true
+	}
+}
diff --git a/packages/tree-select/tsconfig.json b/packages/tree-select/tsconfig.json
index cc8b859680a4f..405a965e3d7bf 100644
--- a/packages/tree-select/tsconfig.json
+++ b/packages/tree-select/tsconfig.json
@@ -1,7 +1,36 @@
 {
-	"extends": "@automattic/calypso-build/tsconfig",
-	"exclude": [ "node_modules" ],
 	"compilerOptions": {
-		"allowJs": true
-	}
+		"target": "ES5",
+		"lib": [ "ES2015" ],
+		"module": "ESNEXT",
+		"allowJs": false,
+		"declaration": true,
+		"declarationMap": true,
+		"declarationDir": "dist/types",
+		"rootDir": "src",
+		"outDir": "dist/esm",
+
+		"strict": true,
+		"noUnusedLocals": true,
+		"noUnusedParameters": true,
+		"noImplicitReturns": true,
+		"noFallthroughCasesInSwitch": true,
+
+		"moduleResolution": "node",
+		"esModuleInterop": true,
+		"downlevelIteration": true,
+
+		"forceConsistentCasingInFileNames": true,
+
+		"importsNotUsedAsValues": "error",
+
+		"typeRoots": [ "../../node_modules/@types" ],
+		"types": [],
+
+		"noEmitHelpers": true,
+		"importHelpers": true,
+
+		"composite": true
+	},
+	"files": [ "src/index.ts" ]
 }
diff --git a/packages/tsconfig.json b/packages/tsconfig.json
index 7751cf2fa3ee5..b0c98904b3a25 100644
--- a/packages/tsconfig.json
+++ b/packages/tsconfig.json
@@ -28,6 +28,7 @@
 		{ "path": "./react-i18n" },
 		{ "path": "./search" },
 		{ "path": "./shopping-cart" },
+		{ "path": "./tree-select" },
 		{ "path": "./wpcom-checkout" }
 	]
 }