The 57-year-old Arians joined the Steelers as the wide receivers coach in 2004 and was promoted to offensive coordinator in 2007.
Tomlin announced the move in a statement Friday, lauding Arians for "helping lead our offense to new heights."
"I am grateful to Bruce for contributing to our success and wish him nothing but the best in his retirement," Tomlin said.
Arians entered the NFL as a running backs coach for the Kansas City Chiefs in 1989 and served as Peyton Manning's first quarterback coach. His NFL resume also includes stints with the New Orleans Saints and Cleveland Browns.
Copyright 2012 by The Associated Press