Redfearn will be the U18s coach at Elland Road and will start the role following York's home game with Blue Square Premier leaders Burton Albion on New Year's Day.
In an academy restructure at the League One club, Daral Pugh steps up to become assistant academy manager.
City chairman Jason McGill said: "We are obviously disappointed to lose Neil, but we recognise that a position at Leeds United is a great opportunity for him.
"Neil has made a really positive contribution at York City and has helped revitalise our youth system while forging a good relationship with our centre of excellence."