The Cowboys announced Sunday the team opted to part ways with Garrett. The coach's contract was set to expire Jan. 14.
"We are extremely grateful to Jason Garrett for his more than 20 years of service to the Dallas Cowboys as a player, assistant coach and head coach," team owner and general manager Jerry Jones said in a statement. "His level of commitment, character and dedication to this organization has been outstanding at every stage of his career."
Garrett's exit was anticipated since the regular season concluded last week, but the Cowboys had yet to officially announce the decision until Sunday night. Dallas interviewed former Cincinnati Bengals head coach Marvin Lewis and ex-Green Bay Packers coach Mike McCarthy for its head coaching vacancy over the weekend.
The split between Garrett and the Cowboys was sensitive for Jones. Jones and Garrett, who was also a backup quarterback and assistant coach for the Cowboys, maintained a strong relationship over the years.
The Cowboys ended the season with a 47-16 victory over the Washington Redskins. After the regular-season finale, Jones declined to part ways with Garrett.
"There's no door shut here tonight," Jones told reporters last Sunday. "None, anywhere, is shut. This is not what this is about. ... I'm not doing that here."
Since becoming the Cowboys' interim head coach in November 2010, Garrett has posted an 85-67 record with the franchise. Dallas won the NFC East in three of the last six seasons but never advanced past the divisional round.
The Cowboys missed the postseason this year and finished with an 8-8 record for the fourth time in Garrett's nine seasons as coach. He will finish as the second-longest-tenured and second-winningest coach in franchise history to Tom Landry.