The presenting duo will appear exclusively on the channel until December 2013 under the new deal.
During this time, the pair will host new editions of reality shows I'm A Celebrity...Get Me Out Of Here! and Britain's Got Talent, as well as a tenth series of Takeaway.
The variety programme last aired in 2009 and was put on hiatus while Ant & Dec launched family gameshow Push The Button.
"Ant and Dec remain at the very top of their game as two of the nation's most popular television stars," ITV controller Peter Fincham said in a statement.
"Their ability to connect with our audience is unrivalled and I'm delighted that we're extending our exclusive partnership with them both for a further two years."
Anthony 'Ant' McPartlin added: "We are really pleased to sign with ITV for another two years and continue to make the programmes we love with the channel."
Declan 'Dec' Donnelly, meanwhile, promised not to disappoint fans with the relaunch of Takeaway, saying: "We always said we would bring back Saturday Night Takeaway, so we're particularly delighted plans are now in place. We have lots of fresh and exciting ideas for the brand new series."
Ant & Dec joined ITV in 1998 to present breakfast shows SM:TV and CD:UK. They have been exclusively signed to the broadcaster since 2000.
> Ant and Dec: 'We'll never go solo'
Watch a clip from Ant & Dec's Saturday Night Takeaway below: