As of 2015, you can activate traditional American Express credit cards by calling 888-263-8774 or by going online to AmericanExpress.com, according to American Express. Activate prepaid American Express cards by calling 866-207-7970 or by going online to Serve.com.
To activate a traditional credit card online, click the Start Here link next to the Don't Have an Online Account prompt under the Log In to Your Online Account heading. The first step in the online registration process requires the 15-digit credit card number and the four-digit card ID, notes American Express. Choose account preferences in step two and select card benefits in step three.
To activate a credit card via the telephone, you must have the credit card number, the four-digit security code and the card's expiration date, advises American Express.
To activate a prepaid American Express card online, click the Register Your Card link located on the top right of the Serve.com homepage, instructs the official website. You are asked for the card number and security code, as well as personal information.
Activate gift cards by following the instructions included with the card, explains American Express. To activate a gift card via telephone, you must have the CID found on the front of the card. Additional identification is also required, including your home telephone number, ZIP code and date of birth.