"There's so many reasons for the decision, but family is the (biggest) one," he said. "Somehow, some way I'm going to be in touch with the game. I'm not leaving the Valley."
Cardinals general manager Steve Keim said the search for a new coach will begin immediately. "We've leave no stone unturned," he said.
"We had some special moments: A lot of wins and battled through adversity together. There's no doubt he'll hold a special place in my heart," Keim said of Arians.
"Steve and I, we love him, and we want him to have a great retirement... We appreciate everything he's done," Cardinals president Michael Bidwill said, adding the Cardinals would begin to make requests to interview potential replacements immediately after the press conference.
Ian Rapoport of NFL Network reported the Cardinals have already asked permission to talk to Vikings offensive coordinator Pat Shurmur. ESPN's Adam Schefter said the Cardinals have reached out to the Eagles about interviewing quarterbacks coach John DeFilippo.
Arians recorded his 50th win as Cards head coach Sunday at Seattle to set a new franchise record. He is a two-time NFL Coach of the Year -- with the Indianapolis Colts in 2012 and the Cardinals in 2014. He led the Cardinals to a franchise-best 13-3 record in 2015 when the team made its second-ever NFC Championship Game appearance.
Arians guided the Cardinals to an 8-8 record in 2017 despite losing star running back David Johnson, quarterback Carson Palmer and several other key players to injury during the season.
Arians has over 40 years of coaching experience. He was the head coach at Temple University from 1983-88 and won two Super Bowls as a member of the Pittsburgh Steelers coaching staff. He helped guide the Steelers past the Cardinals in Super Bowl XLIII when he was Pittsburgh's offensive coordinator.