Yes, it is. As one of the top payment methods in the US, American Express's reputation speaks for itself. Amex itself uses features like multiple security codes for cards, both a CVV and a CIP, and has its own version of 3-D Secure called SafeKey. The best AMEX casinos will also have their own security features, such as requiring you to verify your ID before processing your transactions, and 2-factor authentication for logins. Security is certainly among the benefits of Amex casinos.