The South Africa international has refused to sign an extension to his Everton contract, which was due to expire at the end of the season, and will now join Tottenham in the current transfer window.
He revealed the news on Twitter, writing: 'To end speculation I am going to Spurs. I've had brilliant years at Everton and it will always be a special place in my heart.'
On the move: Steven Pienaar will soon be lining up in the same side as Aaron Lennon
Pienaar arrived at Tottenham's training ground on Tuesday to finalise his £3million switch.
The 28-year-old midfielder underwent a medical before putting pen to paper on a four-year contract.
Spurs beat off competition from Chelsea to land Pienaar, who failed to agree personal terms at Stamford Bridge.
That does not appear to be a problem with Tottenham, who nevertheless risked missing out on the South Africa star by initially refusing to meet Everton's asking price.
The clubs came to an agreement on Monday night, with Spurs eventually matching Chelsea's bid for the player.
Once all the paperwork is complete, Pienaar will become their second January signing, with international team-mate Bongani Kumalo having already penned a pre-contract agreement.
Pienaar later revealed on Twitter that he will wear the No 40 shirt at White Hart Lane.
Everton decided to sell the influential playmaker, rather than lose him on a free transfer when his contract expired in the summer.
A Toffees statement on Monday night read: 'Everton can confirm they have agreed terms with Tottenham over the possible transfer of Steven Pienaar. Confirmation of the agreement with the north London club comes just days after a bid for the South African international was accepted from Chelsea.'
Pienaar joined Everton on loan from Borussia Dortmund in 2007 and the move was made permanent the following year for £2m.
Pienaar switch to Tottenham back on after Everton accept improved £3m bidDistin dejected at Pienaar's imminent Everton exit and fears others could followPienaar to renew talks with Chelsea as Everton reject offer from TottenhamClub-by-club guide to every Premier League transfer deal during January
Explore more:Places: South Africa