The club confirmed the news on their official Twitter handle as well as on their official website.
The tweet read:
The official statement from the club read: "We are delighted to announce the signing of Moussa Sissoko from Newcastle United.
"The France international has signed a contract with the Club until 2021 and will wear the number 17 shirt."
The midfielder seemed delighted after joining the club. He said: "I'm very happy, very proud to be here. I am in the prime of my career and I want to play for a big team, I have the chance now with Tottenham so I'm looking forward and I hope we will do well in the Premier League and in the Champions League also.
"I've said a lot of times that I want to play in the Champions League so that's one of the reasons why I came here - to have the possibility and the chance to play this year.
"I will fight every day at the training ground and then in the games and give my best for this team. I hope we will all do well together."
Another driving force which convinced Sissoko to join Spurs was his French teammate Hugo Lloris. Sissoko continued: "He's a good friend for me. When we are with the national team we speak a lot, we laugh a lot.
"He's a great player and when he spoke to me about this club he told me that it's amazing and everything is here for me to play some good games and to fight with the best teams in England. Today I'm happy and he's happy because we will play together in the Premier League."
Earlier during the day another English club Everton were very close to sign the player and it was being speculated that the midfielder would have his medical at Goodison Park.
Tottenham hijacked the deal at the last moment and went ahead and signed the player.