Originally Posted by
sigma421
Not quite sure I agree here. I managed to use an Amex in plenty of 7-11 locations and a few independent restaurants in Seoul. Online use (including for food delivery services etc.) is a total pain as each bank seems to operate their own payment gateway.
You won't be completely shut out with AMEX like you would in many other countries, but Amex acceptance cannot even compare to Visa and MC in Korea.