The 21-year-old is the third player to sign for Spurs on Friday after the club also announced deals for Erik Lamela and Vlad Chiriches earlier in the day, with Gareth Bale expected to join Real Madrid before the transfer window shuts next week.
"We are delighted to announce that we have reached agreement with Ajax for the transfer of Christian Eriksen," the club confirmed on their official Twitter account.
"Everyone has followed the development of Spurs and it's something I want to be part of", the player told the club's official website.
The Denmark international moved to Ajax in 2008, and played a total of 161 games for the Eredivisie club scoring 33 times.
