International captain Greg Norman also picked Adam Scott, perhaps a bigger surprise because the 29-year-old Australian is going through his worst year as a professional and has slipped to No. 53 in the world ranking.
Ishikawa has won four times in the last calendar year, including the Fujisankei Classic on the Japan Golf Tour last week to move up to No. 47.
U.S. captain Fred Couples used his two picks on U.S. Open champion Lucas Glover and Hunter Mahan. They also were captains picks for the Presidents Cup two years ago.
The Presidents Cup will be played Oct. 8-11 at Harding Park in San Francisco.