The announcement will be made live on Golf Channel at 1 p.m. ET.
In July, Watson confirmed that Andy North would serve as an assistant at Gleneagles. North is a two-time U.S. Open champion who has been working as a commentator for ESPN.
Watson has not said how many assistant captains he will have when the U.S. team looks to win the cup on foreign soil for the first time since 1993 – when Watson also served as captain.