The striker has signed on a five-year deal for a fee of £6m, with a further £1m based on appearances.
The 21-year-old former Charlton trainee made 104 appearances for the Hammers, scoring 41 goals. The Beckton-born striker also enjoyed a prolific seven-month loan spell at Bournemouth during season 2000-01 where he scored 19 goals in 31 appearances.
Reacting to the signing of Defoe at Spurs Lodge, first team coach Chris Hughton agreed that it is a fantastic coup for the club.
"Yes, very much so," he responded. "Anyone who has followed his career will know the quality of the player. I remember seeing him many years ago at Academy level, he was a great prospect then and he has taken that through to the present day."
On completing the transfer, Defoe expressed his excitement at signing and told our mobile phone service spurs (((on!))) that he looking forward to playing with former West Ham teammate Fredi Kanoute again.
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The exciting deadline day capture of Defoe is our second of the January transfer window following the recruitment of Michael Brown from Sheffield United at the beginning of the month. The combative midfielder has since made three first team appearances, making his debut in the 2-1 win over Liverpool at the Lane.
Also on the move during the window was Milenko Acimovic, who joined French side Lille on a six-month loan deal after struggling to establish a first team squad place this season, while Jonathan Blondel has returned to his homeland to play for Club Bruge after the 19-year-old found it difficult to settle following his 2002 switch from Royal Excelsior Mouscron.
On the conclusion of his year-long loan stint at the club from Shimizu S-Pulse, Kazuyuki Toda departed for Dutch side Den Haag after making four first team appearances last season. January also saw the return of Mark Yeates from a successful two-month spell at Brighton and the attacking midfielder has been named in the last two first team squads.
Jermain Defoe has signed for Spurs from West Ham with Bobby Zamora heading in the opposite direction.