Assou-Ekotto, the 22-year-old left back, said: "It wasn't crucial that Tottenham were in the UEFA Cup. I knew about Edgar Davids and I wanted to come to the Premiership and to Spurs."
Sporting Director Damien Comolli said: "He was consistent in his commitment to us in the negotiations we had with Lens despite a lot of interest from other clubs and Lens being reluctant to let him go."
After breaking into the Lens first team with three appearances in 2003-04, he made 29 starts in 2004-05 and 33 starts in 2005-06.
Martin Jol insisted in The Times today that there will be more new faces arriving at White Hart Lane this summer.
Spurs also announced that agreements had been reached with Birmingham City for the transfer of Irish international full back Stephen Kelly and with Dutch team Willem II for the transfer of Mounir El Hamdaoui.