The Dutchman, who was close to joining Everton in January, has signed a four-year deal to become Chris Hughton's sixth summer signing
The 23-year-old becomes the latest arrival in a busy few weeks at Carrow Road, joining fellow new recruits Javier Garrido, Ricky van Wolfswinkel, Nathan Redmond, Carlo Nash and Martin Olsson.
Fer was close to joining Everton in January before the move was scuppered and Norwich manager Chris Hughton has spoken of his delight at capturing the midfielder.
"We are really pleased to have acquired the signature of a player with the qualities that Leroy has," Chris Hughton told the club's official website.
"He's a very versatile Dutch international and at 23 he has that pleasing balance of having acquired experience playing over 100 games in the Dutch League - but still having plenty of time ahead of him to continue his development as a player here with us at Norwich City."
Fer has played for the Netherlands on two occasions and featured in every game for the Under-21s in this year's European Championship, which ended in a semi-final defeat to Italy.