The 30-year-old Dempsey played for the New England Revolution from 2004-06 before joining Fulham in 2007. He moved to Tottenham last summer and scored 12 goals in 43 games, but wasn't a regular.
"We have reached agreement with Major League Soccer for the transfer of Clint Dempsey," Spurs said in a statement Saturday. "We wish Clint every success for the future."
Tottenham didn't say what team Dempsey was going to, but reports had him linked to the Seattle Sounders. The Sounders cleared one of their three designated player slots earlier this week when midfielder Shalrie Joseph restructured his contract to no longer be counted as a designated player.
The team website also asked fans to arrive 15 minutes early to Saturday night's game against FC Dallas for what the club called a "special presentation."
Dempsey raved about Seattle when the city hosted the U.S. against Panama in a World Cup qualifier in June.
"It's great to see the game is building and there are markets like this where people have so much passion for the game," he said.
A star for the U.S. national team, Dempsey wasn't a regular in Andre Villas-Boas' starting lineup. Even so, his move is somewhat surprising because Tottenham could also lose forward Gareth Bale this off-season to Real Madrid.
One of the most successful Americans to play in England's top league, Dempsey was first sold from the Revolution to Fulham in 2007. Dempsey spent five years playing at Craven Cottage, where he scored 50 goals in 184 league appearances and became a fan favourite. Last year with Tottenham, Dempsey scored seven goals in 29 Premier League matches, scored three times in two FA Cup matches and had two more goals in 10 other games.
As his stock in Europe rose, so did Dempsey's role on his national team. He's played in eight games in 2013 for the United States and scored five times. His next international appearance for the Americans will be his 100th, and he's served as the U.S. captain most of this year when Landon Donovan was out.
Dempsey came to England as an attacking midfielder but has developed into a potent forward in recent seasons, starting up front for the U.S. too.