Arians, 59, had been with the Steelers since 2004, serving as wide receivers coach before becoming offensive coordinator in 2007.
This past season Pittsburgh's offense was 12th in the NFL in yards per game and tied for 21st in points.
"I appreciate his efforts over the past five years as the team's offensive coordinator and for helping lead our offense to new heights during his time with the Steelers," Coach Mike Tomlin said in a statement released by the team. "I am grateful to Bruce for contributing to our success and wish him nothing but the best in his retirement."
Arians began his coaching career in 1975 as a graduate assistant at Virginia Tech, where he had played quarterback. He was the head coach at Temple from 1983-88, going 21-45.
He joined the NFL coaching ranks in 1989 with Kansas City and was on staffs at Indianapolis and Cleveland before moving to Pittsburgh.