Financial terms were not disclosed. Time says it expects the acquisition of American Express Publishing Corp. to close in the last three months of this year.
That's about the same time Time Warner Inc. will spin off Time Inc. into a separate company, leaving Time Warner to concentrate on its TV networks and Warner Bros studio.
Time and American Express have been partners for the past 20 years, with Time providing management services to American Express.
Time magazines include "Sports Illustrated" and "People" as well as its namesake.
Shares of American Express are up 82 cents to $74.48.