diff --git a/.changeset/happy-socks-grab/changes.json b/.changeset/happy-socks-grab/changes.json
new file mode 100644
index 000000000..9bc96efcd
--- /dev/null
+++ b/.changeset/happy-socks-grab/changes.json
@@ -0,0 +1,52 @@
+{
+  "releases": [
+    { "name": "@emotion/hash", "type": "patch" },
+    { "name": "@emotion/memoize", "type": "patch" },
+    { "name": "@emotion/weak-memoize", "type": "patch" }
+  ],
+  "dependents": [
+    {
+      "name": "babel-plugin-emotion",
+      "type": "patch",
+      "dependencies": [
+        "@emotion/serialize",
+        "@emotion/hash",
+        "@emotion/memoize"
+      ]
+    },
+    {
+      "name": "@emotion/cache",
+      "type": "patch",
+      "dependencies": ["@emotion/hash", "@emotion/weak-memoize"]
+    },
+    {
+      "name": "@emotion/serialize",
+      "type": "patch",
+      "dependencies": ["@emotion/hash", "@emotion/memoize"]
+    },
+    {
+      "name": "@emotion/is-prop-valid",
+      "type": "patch",
+      "dependencies": ["@emotion/memoize"]
+    },
+    {
+      "name": "emotion-theming",
+      "type": "patch",
+      "dependencies": ["@emotion/weak-memoize"]
+    },
+    {
+      "name": "@emotion/primitives",
+      "type": "patch",
+      "dependencies": [
+        "babel-plugin-emotion",
+        "@emotion/is-prop-valid",
+        "emotion-theming"
+      ]
+    },
+    {
+      "name": "@emotion/styled-base",
+      "type": "patch",
+      "dependencies": ["@emotion/serialize", "@emotion/is-prop-valid"]
+    }
+  ]
+}
diff --git a/.changeset/happy-socks-grab/changes.md b/.changeset/happy-socks-grab/changes.md
new file mode 100644
index 000000000..730775aa7
--- /dev/null
+++ b/.changeset/happy-socks-grab/changes.md
@@ -0,0 +1 @@
+Add TS types to util packages - hash, memoize & weak-memoize
diff --git a/packages/hash/package.json b/packages/hash/package.json
index 5cbbdd273..422830a58 100644
--- a/packages/hash/package.json
+++ b/packages/hash/package.json
@@ -4,6 +4,7 @@
   "description": "A MurmurHash2 implementation",
   "main": "dist/hash.cjs.js",
   "module": "dist/hash.esm.js",
+  "types": "types/index.d.ts",
   "license": "MIT",
   "repository": "https://github.com/emotion-js/emotion/tree/master/packages/hash",
   "publishConfig": {
@@ -11,10 +12,17 @@
   },
   "files": [
     "src",
-    "dist"
+    "dist",
+    "types"
   ],
+  "scripts": {
+    "test:typescript": "dtslint types"
+  },
+  "devDependencies": {
+    "dtslint": "^0.3.0"
+  },
   "browser": {
     "./dist/hash.cjs.js": "./dist/hash.browser.cjs.js",
     "./dist/hash.esm.js": "./dist/hash.browser.esm.js"
   }
-}
\ No newline at end of file
+}
diff --git a/packages/hash/types/index.d.ts b/packages/hash/types/index.d.ts
new file mode 100644
index 000000000..872aa0bef
--- /dev/null
+++ b/packages/hash/types/index.d.ts
@@ -0,0 +1 @@
+export default function murmurhash2_32_gc(str: string): string
diff --git a/packages/hash/types/tests.ts b/packages/hash/types/tests.ts
new file mode 100644
index 000000000..fe6444e8a
--- /dev/null
+++ b/packages/hash/types/tests.ts
@@ -0,0 +1,15 @@
+import hash from '@emotion/hash'
+
+// $ExpectType string
+hash('color: hotpink;')
+
+// $ExpectError
+hash()
+// $ExpectError
+const hashed2: number = hash('color: hotpink;')
+// $ExpectError
+hash(42)
+// $ExpectError
+hash({})
+// $ExpectError
+hash('color: hotpink;', 'background-color: #fff;')
diff --git a/packages/hash/types/tsconfig.json b/packages/hash/types/tsconfig.json
new file mode 100644
index 000000000..9ff7ed289
--- /dev/null
+++ b/packages/hash/types/tsconfig.json
@@ -0,0 +1,26 @@
+{
+  "compilerOptions": {
+    "baseUrl": "../",
+    "forceConsistentCasingInFileNames": true,
+    "lib": [
+      "es6",
+      "dom"
+    ],
+    "module": "commonjs",
+    "noEmit": true,
+    "noImplicitAny": true,
+    "noImplicitThis": true,
+    "strict": true,
+    "strictNullChecks": true,
+    "strictFunctionTypes": true,
+    "target": "es5",
+    "typeRoots": [
+      "../"
+    ],
+    "types": []
+  },
+  "include": [
+    "./*.ts",
+    "./*.tsx"
+  ]
+}
diff --git a/packages/hash/types/tslint.json b/packages/hash/types/tslint.json
new file mode 100644
index 000000000..b9706ef70
--- /dev/null
+++ b/packages/hash/types/tslint.json
@@ -0,0 +1,25 @@
+{
+    "extends": "dtslint/dtslint.json",
+    "rules": {
+        "array-type": [
+            true,
+            "generic"
+        ],
+        "import-spacing": false,
+        "semicolon": false,
+        "whitespace": [
+            true,
+            "check-branch",
+            "check-decl",
+            "check-operator",
+            "check-module",
+            "check-rest-spread",
+            "check-type",
+            "check-typecast",
+            "check-type-operator",
+            "check-preblock"
+        ],
+
+        "no-unnecessary-generics": false
+    }
+}
diff --git a/packages/memoize/package.json b/packages/memoize/package.json
index 329dcdcda..8207ff58f 100644
--- a/packages/memoize/package.json
+++ b/packages/memoize/package.json
@@ -4,17 +4,25 @@
   "description": "emotion's memoize utility",
   "main": "dist/memoize.cjs.js",
   "module": "dist/memoize.esm.js",
+  "types": "types/index.d.ts",
   "license": "MIT",
   "repository": "https://github.com/emotion-js/emotion/tree/master/packages/memoize",
+  "scripts": {
+    "test:typescript": "dtslint types"
+  },
   "publishConfig": {
     "access": "public"
   },
+  "devDependencies": {
+    "dtslint": "^0.3.0"
+  },
   "files": [
     "src",
-    "dist"
+    "dist",
+    "types"
   ],
   "browser": {
     "./dist/memoize.cjs.js": "./dist/memoize.browser.cjs.js",
     "./dist/memoize.esm.js": "./dist/memoize.browser.esm.js"
   }
-}
\ No newline at end of file
+}
diff --git a/packages/memoize/types/index.d.ts b/packages/memoize/types/index.d.ts
new file mode 100644
index 000000000..23f3580f1
--- /dev/null
+++ b/packages/memoize/types/index.d.ts
@@ -0,0 +1,3 @@
+type Fn<T> = (key: string) => T
+
+export default function memoize<T>(fn: Fn<T>): Fn<T>
diff --git a/packages/memoize/types/tests.ts b/packages/memoize/types/tests.ts
new file mode 100644
index 000000000..81b32b8ba
--- /dev/null
+++ b/packages/memoize/types/tests.ts
@@ -0,0 +1,7 @@
+import memoize from '@emotion/memoize'
+
+// $ExpectType string[]
+memoize((arg: string) => [arg])('foo')
+
+// $ExpectError
+memoize((arg: number) => [arg])
diff --git a/packages/memoize/types/tsconfig.json b/packages/memoize/types/tsconfig.json
new file mode 100644
index 000000000..9ff7ed289
--- /dev/null
+++ b/packages/memoize/types/tsconfig.json
@@ -0,0 +1,26 @@
+{
+  "compilerOptions": {
+    "baseUrl": "../",
+    "forceConsistentCasingInFileNames": true,
+    "lib": [
+      "es6",
+      "dom"
+    ],
+    "module": "commonjs",
+    "noEmit": true,
+    "noImplicitAny": true,
+    "noImplicitThis": true,
+    "strict": true,
+    "strictNullChecks": true,
+    "strictFunctionTypes": true,
+    "target": "es5",
+    "typeRoots": [
+      "../"
+    ],
+    "types": []
+  },
+  "include": [
+    "./*.ts",
+    "./*.tsx"
+  ]
+}
diff --git a/packages/memoize/types/tslint.json b/packages/memoize/types/tslint.json
new file mode 100644
index 000000000..b9706ef70
--- /dev/null
+++ b/packages/memoize/types/tslint.json
@@ -0,0 +1,25 @@
+{
+    "extends": "dtslint/dtslint.json",
+    "rules": {
+        "array-type": [
+            true,
+            "generic"
+        ],
+        "import-spacing": false,
+        "semicolon": false,
+        "whitespace": [
+            true,
+            "check-branch",
+            "check-decl",
+            "check-operator",
+            "check-module",
+            "check-rest-spread",
+            "check-type",
+            "check-typecast",
+            "check-type-operator",
+            "check-preblock"
+        ],
+
+        "no-unnecessary-generics": false
+    }
+}
diff --git a/packages/weak-memoize/package.json b/packages/weak-memoize/package.json
index 337b7e892..7533b5da6 100644
--- a/packages/weak-memoize/package.json
+++ b/packages/weak-memoize/package.json
@@ -4,17 +4,25 @@
   "description": "A memoization function that uses a WeakMap",
   "main": "dist/weak-memoize.cjs.js",
   "module": "dist/weak-memoize.esm.js",
+  "types": "types/index.d.ts",
   "license": "MIT",
   "repository": "https://github.com/emotion-js/emotion/tree/master/packages/weak-memoize",
+  "scripts": {
+    "test:typescript": "dtslint types"
+  },
   "publishConfig": {
     "access": "public"
   },
+  "devDependencies": {
+    "dtslint": "^0.3.0"
+  },
   "files": [
     "src",
-    "dist"
+    "dist",
+    "types"
   ],
   "browser": {
     "./dist/weak-memoize.cjs.js": "./dist/weak-memoize.browser.cjs.js",
     "./dist/weak-memoize.esm.js": "./dist/weak-memoize.browser.esm.js"
   }
-}
\ No newline at end of file
+}
diff --git a/packages/weak-memoize/types/index.d.ts b/packages/weak-memoize/types/index.d.ts
new file mode 100644
index 000000000..a2b9f0654
--- /dev/null
+++ b/packages/weak-memoize/types/index.d.ts
@@ -0,0 +1,5 @@
+type UnaryFn<Arg, Return> = (arg: Arg) => Return
+
+export default function weakMemoize<Arg extends object, Return>(
+  func: UnaryFn<Arg, Return>
+): UnaryFn<Arg, Return>
diff --git a/packages/weak-memoize/types/tests.ts b/packages/weak-memoize/types/tests.ts
new file mode 100644
index 000000000..72a869db9
--- /dev/null
+++ b/packages/weak-memoize/types/tests.ts
@@ -0,0 +1,36 @@
+import weakMemoize from '@emotion/weak-memoize'
+
+type Foo = { bar: 'xyz' }
+
+declare class Qwe {
+  answer: number
+}
+
+// $ExpectType Array<Foo>
+weakMemoize((arg: Foo) => [arg])({ bar: 'xyz' })
+
+// $ExpectType string[]
+weakMemoize((arg: string) => [arg])('foo')
+
+// $ExpectError
+weakMemoize((arg: Foo) => [arg])(42)
+
+// $ExpectError
+weakMemoize((arg: string) => [arg])
+// $ExpectError
+weakMemoize((arg: number) => [arg])
+// $ExpectError
+weakMemoize((arg: boolean) => [arg])
+// $ExpectError
+weakMemoize((arg: symbol) => [arg])
+// $ExpectError
+weakMemoize((arg: void) => [arg])
+// $ExpectError
+weakMemoize((arg: null) => [arg])
+// $ExpectError
+weakMemoize((arg: undefined) => [arg])
+
+weakMemoize((arg: () => void) => [arg])
+weakMemoize((arg: Map<any, any>) => [arg])
+weakMemoize((arg: Set<any>) => [arg])
+weakMemoize((arg: Qwe) => [arg])
diff --git a/packages/weak-memoize/types/tsconfig.json b/packages/weak-memoize/types/tsconfig.json
new file mode 100644
index 000000000..9ff7ed289
--- /dev/null
+++ b/packages/weak-memoize/types/tsconfig.json
@@ -0,0 +1,26 @@
+{
+  "compilerOptions": {
+    "baseUrl": "../",
+    "forceConsistentCasingInFileNames": true,
+    "lib": [
+      "es6",
+      "dom"
+    ],
+    "module": "commonjs",
+    "noEmit": true,
+    "noImplicitAny": true,
+    "noImplicitThis": true,
+    "strict": true,
+    "strictNullChecks": true,
+    "strictFunctionTypes": true,
+    "target": "es5",
+    "typeRoots": [
+      "../"
+    ],
+    "types": []
+  },
+  "include": [
+    "./*.ts",
+    "./*.tsx"
+  ]
+}
diff --git a/packages/weak-memoize/types/tslint.json b/packages/weak-memoize/types/tslint.json
new file mode 100644
index 000000000..b9706ef70
--- /dev/null
+++ b/packages/weak-memoize/types/tslint.json
@@ -0,0 +1,25 @@
+{
+    "extends": "dtslint/dtslint.json",
+    "rules": {
+        "array-type": [
+            true,
+            "generic"
+        ],
+        "import-spacing": false,
+        "semicolon": false,
+        "whitespace": [
+            true,
+            "check-branch",
+            "check-decl",
+            "check-operator",
+            "check-module",
+            "check-rest-spread",
+            "check-type",
+            "check-typecast",
+            "check-type-operator",
+            "check-preblock"
+        ],
+
+        "no-unnecessary-generics": false
+    }
+}