The deal means the Cowboys now have one of three key players signed to a long-term deal.
Dallas is also trying to sign safety Roy Williams and linebacker Bradie James to long-term deals as well.
Witten was entering the final season of his original four-year contract he signed as a rookie back in 2003.
Two years ago, Witten put together the greatest receiving season by a tight end in Cowboys' history when he earned his first Pro Bowl appearance after catching 87 passes for 980 yards.
He was the first Cowboys tight end to represent the Cowboys in the Pro Bowl since Jay Novacek went to Hawaii in 1995.
Last year he brought in another 66 receptions for 757 yards and also earned a spot in the Pro Bowl.
After being taken in the third round of the 2003 NFL Draft out of Tennessee, Witten tied for fourth in the NFL among all rookies with 35 receptions and was tops among all rookie tight ends.
The timing of Witten's signing was important to the Cowboys and Witten for several reasons.
With the Cowboys expecting to use more two tight end formations this season, he is expected to be an even more critical component in the Cowboys' passing game.
In addition, he's also one of the top pass catching tight ends in the league and with contract talks out of the way, he can now focus squarely on the start of training camp later this week in Oxnard, Calif.