Campbell suffered the injury with 7:46 remaining in the third quarter after he took a shot to the head from blitzing cornerback William Gay.
No flag was thrown, but Gay hit Campbell in the facemask as he came clean on a blitz. The hit led to a fumble, which Pittsburgh's Will Allen recovered and returned to the Browns' 4-yard-line. Ben Roethlisberger hit Emmanuel Sanders for a touchdown on the following play to give Pittsburgh a 20-3 lead.
Campbell was examined on the sideline before he was carted to the locker room, his head slumped as he was driven off. The Browns said he is out for the remainder of the game.
Brandon Weeden replaced Campbell, leaving the Browns with one active quarterback. They have two on the roster, and the third normally is MarQueis Gray, who played at Minnesota last year. But Gray was inactive with a hamstring injury.
Campbell had left the game for a play earlier in the game when he fell on sore ribs after a sack.
In his fourth start, Campbell was 14-for-22 for 124 yards, no touchdowns and no interceptions.