Simons told Tottenham's website: "I'm really happy and can't wait to get going. I've been dreaming of this for a long time.
"It's a great club and when I met the head coach I knew straight away that this was the right place for me.
"I will bring flair to the team but also hard work and discipline. I want to do everything I can to win, for the team and also for the fans."
Frank added: “I’m really pleased we have brought Xavi in - he is a great addition to the squad.
“He is still young, however he already has good experience and, over the past few years, has played a lot of games at the top level.
“Xavi has proven his ability to get goals and assists, both from the No.10 position and left wing. He also has a great eye for his team-mates in terms of unlocking defences, and I know he will come in and be part of a good team that is already working hard together.”