The Belgium international's move will be rubberstamped once he passes his Spurs medical.
Chadli has added to the wealth of playmaking talent, with his versatility in the final third making him a shrewd addition.
Villas-Boas said of the 23-year-old winger: "Chadli's a player we've been following for quite some time and we managed to strike a deal in the last few days.
"He's a player who is extremely versatile and can play in several positions up front. He played with tremendous success on the left for Twente as a winger and as an attacker for Belgium. We look forward to having him on board with us."