The Toffees had accepted a bid - believed to be in the region of £3 million - from Carlo Ancelotti's men for the South African international's services, with Harry Redknapp's side thought to be unwilling to match the Blues' offer.
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However, the White Hart Lane outfit have since agreed a fee with their Goodison Park counterparts for the midfielder, with Pienaar later announcing his plans on Twitter.
"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," he said.
Pienaar, who is out of contract with Everton at the end of the season, asked to be left out of the Everton side for Sunday's 2-2 draw at Liverpool.
"Steven came to see me and said he didn't feel he was in the right place to play... I felt it would be better not to use him if that was the case," Everton boss David Moyes said ahead of the Merseyside derby.
Pienaar also revealed that he will be wearing shirt number 40 for his new side.
