To make room for Smith, the Jaguars placed cornerback Scott Starks on injured reserve with a hamstring injury.
Smith, a third-round draft pick by Pittsburgh in 2006, has played 48 games with 14 starts for the Steelers and Rams. He has 99 tackles, four interceptions and 23 special teams tackles.
Smith played two games for the Rams this season before he was waived Thursday.
Starks played five games for the Jaguars this season and had seven tackles and two special teams tackles.