The 26-year-old has moved north to the KC Stadium, where he will wear the No 8 shirt, after struggling to secure a regular starting place for Spurs under Andre Villas-Boas.
Huddlestone, who has made four appearances for England, played 209 games in all competitions for Tottenham after joining them from Derby in 2005 and scored 15 goals.
Hull have also signed Spurs midfielder Jake Livermore on a season-long loan deal, with the Tigers paying in the region of £5m to secure the pair.
Livermore, 23, made 11 Premier League appearances for Tottenham last season and has had previous loan spells with MK Dons, Crewe, Derby, Peterborough, Ipswich and Leeds.
He has featured once as a substitute for England in the 2-1 win over Italy last August.