The 21-year-old Brazilian midfielder will arrive at White Hart Lane after the conclusion of the Copa Libertadores in South America this summer.
"He is an outstanding young player who we feel has a great future," said Spurs boss Harry Redknapp.
"He is a strong and aggressive midfield player. We are looking forward to having him here with us next season. He has already played for Brazil and captained their youth sides too.
"I went for dinner with Alex Ferguson the other night and he came up with the most amazing statistic. There were around 14 or 15 English players playing in the Champions League last year and over 100 Brazilians.
"When you think it is a European tournament it just shows you the strength in depth and quality of Brazilian footballers and this is one of the brightest prospects to come out of Brazil.
"The chairman has done a terrific job to make this happen. I think there were hard and protracted negotiations so a lot of credit must go to Daniel (Levy).
"There are not too many chairmen that would fly half way around the world to get a deal done and he has gone and flown personally to Brazil twice."