New sigFulham accepted a £7m bid from Villa earlier on Friday and turned down £4.5m from Liverpool but the forward held out for a move that suited him better.
Dempsey joined Fulham in 2007 from New England Revolution, scoring 60 goals in 224 appearances for the Craven Cottage team.
ning Clint Dempsey with Spurs shirt
Clint Dempsey has completed a shock move from Fulham to London rivals Tottenham Hotspur for £6million.
Dempsey arrived on a three-year deal after Aston Villa and Liverpool failed to land the United States forward.