Batch agreed to a one-year, $895,000 deal, including a $50,000 signing bonus.
Batch, 34, is entering his 11th season, his seventh with the Steelers. A native of Pittsburgh, Batch joined the Steelers in 2002 and has played in 22 games, including four starts.
His first four seasons were with the Detroit Lions, where he was a starter most of his time.
Batch suffered a broken clavicle last August, forcing him to spend the season on the injured reserve list. That created the opening for Leftwich to join the team as the backup.
The Steelers would have liked to have Leftwich and Batch back, but they figured Leftwich would find a different team.
Leftwich signed a two-year, $7.5 million deal Monday with the Tampa Bay Buccaneers.