Mercury Cards Activation Activate a Mercury Mastercard credit card online Requires internet access Simply visit www.mercurycards.com/activate to begin. Please have the card number on hand (check out the Mercury Card Rewards Program) To obtain a Mercury Mastercard, you must be 18 years or older and a legal resident of the United States. This is a … Continue reading MercuryCards Activate – How To Activate Mecury Card Guide