The 19-year-old, who featured 24 times in all competitions for NEC last season, has put pen to paper on a four-year deal at Elland Road.
Grot, handed the number 11 shirt, is pleased to have finalised a switch to West Yorkshire and is now looking forward to beginning a new chapter in his career.
"I am very happy, this is such a big club and this is a big step in my career, I am delighted to signed for Leeds United," he told his new side's official website. "It has been my dream to play in England and so to do that at a club like Leeds is really exciting."
Christiansen could hand Grot his debut in Saturday's league meeting with Nottingham Forest at City ground, as the Whites go in search of a third successive away win to begin the new campaign.