Since the bank mainly offers credit cards that belong to the Mastercard network, you'll be able to use your credit cards in any country where Mastercard is accepted. Mastercard is available in over 210 countries, and millions of online (and offline) merchants accept cards in this network. However, if you decide to use your Celtic Bank Mastercard credit card abroad, you need to know that you will incur high foreign transaction fees, and possibly even currency conversion fees. If possible, you should only use no foreign transaction fee credit cards when you're abroad.