The currency in Florida Keys & Key West is the US Dollar.
Save time when you get there and sort your travel money before you jet off. Not sure how many dollars you’ll need? Then, you can always change what you think you’ll need and buy some more when you arrive. There are a few banks in Key West, or if you prefer not to carry any cash at all, debit and credit cards are also widely accepted. Just make sure you let your bank know that you are using your card overseas so you’re aware of any additional fees.