Fichtner had been a staple of head coach Mike Tomlin's staff since 2007, debuting as the club's wide receivers coach before moving on to become the quarterbacks coach in 2010.
The Steelers also parted ways with offensive line coach Shaun Sarrett and defensive backs coach Tom Bradley.
"I want to thank all three of the coaches for their commitment and dedication to the Pittsburgh Steelers," Tomlin said. "They have all played integral roles in our success and I am appreciative of their efforts.
"Personally, Randy and I have been in Pittsburgh since I hired him in 2007, but our relationship began well before that. He has been a friend of mine for years and I wish his family nothing but the best, and I am eternally grateful for our relationship both on and off the field."
Fichtner became a lightning rod for criticism this past season as the Steelers' offense morphed into a one-dimensional, dink-and-dunk passing attack. The team finished the year with the league's fewest rushing yards, while quarterback Ben Roethlisberger averaged a career-low 6.3 yards per pass attempt.
In his year-end news conference, Tomlin vowed to make "some changes in what we do," both in terms of tactics and personnel.
The Steelers won 11 straight games to begin the season, but they lost five of their final six, including on Wild Card Weekend to the Cleveland Browns.