In the English Premier League, the London club finished in 5th place, is set to strengthen their squad for next year with the promising defender Gareth Bale from the Welsh national team and a team from the lower Championship league.
Southampton claims that Tottenham will have to pay £5 million immediately, and in the future, they may have to pay an additional amount that could increase to £10 million.
"I am very excited to play for a club like Tottenham," said the 17-year-old player. "This is a step forward in my career."
Bale, who was especially sought after by London and other English giants, still had a contract with Southampton for another year. Spurs had agreed with Southampton on a £10 million ransom in January when the player himself refused to move to London.
After Southampton failed to secure promotion to the Premier League, the player changed his mind, hoping to establish himself in the main lineup of the Tottenham team.
"I really want to play in the Premier League," added the young footballer. "This is a fantastic opportunity for me. I thought about it for a long time and worked hard, so I think now is the time to change the environment."
"I could have done it in January, but I wanted to help Southampton return to the Premier League. I felt I owed them and therefore did not plan to leave the team in the middle of the season."
Bale made his debut in the Southampton shirt when he was just 16 years old, becoming the second youngest player in the team's history, and this season he was a key player for both Southampton and the Welsh national team.
"We have been monitoring Gareth for a long time and we were very persistent, so we are extremely happy that we managed to attract him to Tottenham," said Spurs' sporting director Damien Comolli.