Terms of the deal have been not announced.
The 6-foot-1, 200-pound Smith played in all 16 regular season games and both playoff games for the San Francisco 49ers in 2011. He recorded 16 tackles and one interception during the regular season. Smith also contributed on special teams with six special teams tackles during the regular season and two during the postseason.
"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 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."
Earlier this offseason the Panthers signed free agent safety Haruki Nakamura from the Baltimore Ravens, another young player who could potentially compete with Sherrod Martin for a starting job. Martin struggled with his tackling last season and that didn't sit well with coach Ron Rivera, who places a huge emphasis on acquiring players who can tackle.
Charles Godfrey is expected to be Carolina's other starting safety after signing a five-year contract extension last year.
Smith spent four seasons with the 49ers after being selected by the team in the third round (75th overall) of the 2008 draft out of Oklahoma.
Smith's best season came in 2010 when he started seven games and produced 37 tackles and one interception on defense and added 14 tackles on special teams. He played in 44 career regular season games with seven starts.
He has career totals of 54 tackles, two interceptions and seven passes defensed.