A few weeks ago, a client needed a second Google AdWords account linked to an existing Analytics account already linked to an AdWords account. As luck would have it, Google just recently made it possible to do this!
2. Next, make sure both AdWords accounts have admin access to your Analytics. To do this, log in to Google Analytics and go to your Dashboard. In the new version, you'll see “Admin” in the top right:
Click Users, then “+ New User”. Make sure the email addresses you use for both AdWords accounts are set as admins here.
3. Then, click the name of the site at the top of the page.
From here, you'll see several options in the secondary menu. Click “Data Sources” and be sure you're in “AdWords”.
If you're logged in under an account that's already linked to Analytics, you should see it listed.
4. Your last and final step is to log in under the unlinked account and follow step 3. Then, click “Link Accounts” and click “Continue” after seeing this screen:
And you're done! There is one important thing to keep in mind: you'll only have statistics for the additional account from the day you go through these steps.