Kreis, who led RSL to the 2013 MLS Cup final where they lost on penalties to Sporting Kanas City on the weekend, will officially begin his role in January 2014.
Kreis will first travel to England to spend time with Manchester City - the majority owners of NYCFC - working closely with manager Manuel Pellegrini, elite development chief Patrick Vieira and director of football Txiki Begiristain.
The former Dallas Burn (FC Dallas) and Real Salt Lake midfielder/forward has been with RSL for near-on seven years and will bring a wealth of experience to New York City according to the clubs sporting director Claudio Reyna.
"Jason is one of the true pioneers of Major League Soccer, and a leader any team would be proud to have at the helm," he said.
"His skills and experience, together with his commitment to quality football make him the ideal choice to lead New York City FC in its first season and beyond.
"He has already left a historic mark on the league, both as a player and coach and we have every confidence in him continuing to do so at New York City FC."
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