The north London club will pay Marseille around £11m and the France Under-21 international is due to officially become a Spurs player in the next few days.
N'koudou signed for Marseille from Nantes one year ago for just £1m.
The young winger impressed in his single season at the Stade Velodrome, playing 41 times and scoring 10 goals.
Are Spurs about to sign a player with huge potential?