diff --git a/types/chrome/index.d.ts b/types/chrome/index.d.ts
index 016458df3a..3a6bf635a3 100644
--- a/types/chrome/index.d.ts
+++ b/types/chrome/index.d.ts
@@ -1266,6 +1266,9 @@ declare namespace chrome.contextMenus {
  * Permissions:  "cookies", host permissions
  */
 declare namespace chrome.cookies {
+    /** A cookie's 'SameSite' state (https://tools.ietf.org/html/draft-west-first-party-cookies). 'no_restriction' corresponds to a cookie set with 'SameSite=None', 'lax' to 'SameSite=Lax', and 'strict' to 'SameSite=Strict'. 'unspecified' corresponds to a cookie set without the SameSite attribute. **/
+    export type SameSiteStatus = 'unspecified' | 'no_restriction' | 'lax' | 'strict';
+
     /** Represents information about an HTTP cookie. */
     export interface Cookie {
         /** The domain of the cookie (e.g. "www.google.com", "example.com"). */
@@ -1288,6 +1291,11 @@ declare namespace chrome.cookies {
         httpOnly: boolean;
         /** True if the cookie is marked as Secure (i.e. its scope is limited to secure channels, typically HTTPS). */
         secure: boolean;
+        /**
+         * The cookie's same-site status (i.e. whether the cookie is sent with cross-site requests).
+         * @since Chrome 51.
+         */
+        sameSite: SameSiteStatus
     }
 
     /** Represents a cookie store in the browser. An incognito mode window, for instance, uses a separate cookie store from a non-incognito window. */
@@ -1334,6 +1342,11 @@ declare namespace chrome.cookies {
         httpOnly?: boolean;
         /** Optional. Whether the cookie should be marked as Secure. Defaults to false.  */
         secure?: boolean;
+        /**
+         * Optional. The cookie's same-site status. Defaults to "unspecified", i.e., if omitted, the cookie is set without specifying a SameSite attribute.
+         * @since Chrome 51.
+         */
+        sameSite?: SameSiteStatus
     }
 
     export interface Details {
diff --git a/types/sinon-chrome/sinon-chrome-tests.ts b/types/sinon-chrome/sinon-chrome-tests.ts
index ab5f050f52..52b6206a03 100644
--- a/types/sinon-chrome/sinon-chrome-tests.ts
+++ b/types/sinon-chrome/sinon-chrome-tests.ts
@@ -64,7 +64,8 @@ chromeStub.registerPlugin(new chromeStub.plugins.CookiePlugin(
             secure: false,
             session: false,
             storeId: '0',
-            value: 'COOKIE_VALUE'
+            value: 'COOKIE_VALUE',
+            sameSite: 'unspecified'
         },
         {
             domain: 'other-domain.com',
@@ -75,7 +76,8 @@ chromeStub.registerPlugin(new chromeStub.plugins.CookiePlugin(
             secure: false,
             session: true,
             storeId: '0',
-            value: '123'
+            value: '123',
+            sameSite: 'unspecified'
         }
     ]
 ));