Question: Can I Use Mastercard  at Costco?

Answer: No, you can not use Mastercard credit card at Costco.  You can only use Visa credit cards.  Costco switched from American Express Credit Card to Visa as exclusive credit card payment on June 20, 2016.

Before June 20, 2016, you could only use American Express credit cards.  After June 20, 2016, you could only use Visa credit cards, along with cash, checks, debit and ATM cards, Electronic benefit transfer (EBT) and Costco Cash cards.

You can still use Mastercard at Costco.com website but not in-store purchase.

Costco Credit Cards are issued by Citibank.