The details of the deal for the 22-year-old, who starred on loan at Swansea in the Premier League last season, have not yet been disclosed.
Sigurdsson is Andre Villas-Boas' first signing as Spurs head coach.
The former Chelsea boss was only appointed as Harry Redknapp's successor on Tuesday, but has moved quickly to bring Sigurdsson to White Hart Lane.
The move secures the Icelander's return to the Premier League, where he impressed so much during his spell at the Liberty Stadium.
The Liverpool 2013/14 soccer jersey is available for pre-order. The Reds are eager to compete for silver next season.
The adidas Nitrocharge is the most talked about new cleat in years. It was released on May 15 and will take your pitch by storm.
The new PUMA evoSPEED 1.2 FG. A great new soccer cleat with classic look and first time for PUMA to be on the cleat.
Chelsea won the Europa League on Wednesday. The Blues defeated Benfica 2-1 on injury time goal from Ivanovic.
Bayern Munich are kings of Germany and hope to be crowned kings of Europe at Wembley later this month!
One of the top soccer cleats for control the Nike CTR360 will not let you down on the field in tight spaces.
Borussia Dortmund hears Wembley Calling and are headed to London for the Champions League final.
The Juventus jersey for the 2013/14 was released earlier this week. Be the first to wear the colors of the Old Lady.
The push for more color on their cleats, adidas has added the infrared colorway to the adiZero f50 Line.
adidas has added some color to the Predator line with this new colorway. Released on May 17. Be the first to own a pair.