A six-year NFL veteran at linebacker who hasn't played in a regular-season game since 2006, Stewart is attempting to reinvent himself with the Steelers. A source told FOXSports.com that Stewart was signed to take the place of incumbent Jared Retkofsky, who was released last week.
Stewart was in training camp with Arizona and Dallas the past two seasons but didn't make the final roster.
Stewwart, 30, was a 2001 fourth-round draft pick by Atlanta. He has 60 career starts and was a core special-teams player for the Falcons until 2004 and then Cleveland (2005-06). Stewart, who played at Vanderbilt, was considered one of the top long-snappers in his draft class.
The Steelers have made upgrading last year's poor special-teams unit an offseason priority.