Bell, 29, likely will soon get elevated to the 53-man roster, a source told ESPN's Adam Schefter.
The addition of Bell comes after the Ravens lost third-string running back Justice Hill to an Achilles injury, placing him on injured reserve Wednesday. Baltimore already had lost starting running back J.K. Dobbins when he tore the ACL in his left knee in the preseason finale.
In 2019, the Ravens had an opportunity to sign Bell in free agency but chose to add Mark Ingram, who played in Baltimore for two seasons before getting released in January.
After gaining over 1,000 yards rushing in three of his five seasons with the Pittsburgh Steelers, Bell hasn't been the same playmaker since sitting out the 2018 season. Last season, he totaled 328 yards rushing and two touchdowns with the New York Jets and Kansas City Chiefs.
The Ravens also signed running back Trenton Cannon to their 53-man roster Wednesday. Cannon, 27, had 33 yards on 10 carries for the Carolina Panthers last season while also handling some kickoff return duties. Baltimore also released safety Jordan Richards off the practice squad.
Bell isn't the first former Pro Bowl player to get signed to the Ravens' practice squad. Last season, Baltimore added wide receiver Dez Bryant to its practice squad before promoting him to the 53-man roster.