Cotchery, 29, is expected to compete with Emmanuel Sanders for the team's No. 3 wide receiver job. Steelers coach Mike Tomlin has expressed concern over whether Sanders can remain healthy for an entire season.
In his first season with the Steelers, Cotchery caught 16 passes, his lowest total since his 2004 rookie season. But Cotchery made an impact in the second half of the season when Hines Ward was being phased out of the offense. In the final eight games, Cotchery had 15 catches for 227 yards and two touchdowns.
Wednesday marks the second straight day the Steelers have signed a player after not adding anyone in the first 28 days of free agency. Pittsburgh signed backup tight end Leonard Pope on Tuesday.
Cotchery drew interest from the Rams and Chiefs before returning to Pittsburgh.
Information from ESPN.com's Jamison Hensley contributed to this report.