The 48-year-old guided the Texan franchise to their first post-season appearance since 2009, where they were only narrowly and controversially ousted by the Green Bay Packers in the divisional showdown.
Garrett, who took the role on an interim basis in 2010 when he replaced Wade Phillips, helped the Cowboys to clinch this season’s??NFC East division title with a 12-4 record.
He said: “We started something four years ago when I became the head coach.
“It’s a word I think about really each and every day when I wake up and throughout the day, it’s ‘build.’ We want to build a football team that everyone who is associated with our football team is proud of. I feel like we’ve done that.
“The work is not done. We’re excited about the opportunities in 2015 to build on some of the things we did this past season.”
Two of Garrett’s staff, defensive co-ordinator??Rod Marinelli and offensive play-caller Scott Linehan, have also signed three-year deals.