A third-round draft pick out of Oklahoma in 2008, Smith played in both of the 49ers' playoff games last season, breaking up a pass in a pivotal spot during their NFC Divisional Playoff victory over the New Orleans Saints.
During the regular season he played in all 16 games in a reserve role, recording 16 tackles, an interception and three passes defensed. The interception sealed a 13-8 victory over the Cincinnati Bengals.
"Reggie has been on our radar since the beginning of free agency and is a player we think can come in and compete at safety," Carolina Panthers general manager Marty Hurney said. "We brought him in for a visit Tuesday, and it worked out. He is another player we've added to increase the competition."
Smith played safety for the 49ers the last three seasons after playing cornerback as a rookie. He has contributed on special teams throughout his NFL career, with 29 special teams tackles in 44 games.
He started the final seven games of the 2010 season at strong safety – the only time he's started in his NFL career – and recorded 37 tackles with an interception and four passes defensed.