Stewart's 26-carry effort keyed Carolina's ball-control offense and led to three field goals by John Kasay, whose first field goal Sunday was the 400th of his NFL career.
Matt Moore, starting for the injured Jake Delhomme (broken finger), completed 14-of-20 passes for 161 yards, no touchdowns and one interception. Steve Smith caught three passes for 78 yards for the Panthers (5-7), who have split their last six games.
Tampa Bay's Josh Freeman finished 23-of-44 for 321 yards with the five interceptions, two by Jon Beason.
Cadillac Williams rushed for 92 yards on 17 carries.
Antonio Bryant made five receptions for 116 yards, while Connor Barth booted two field goals for the Buccaneers (1-11), who have lost four in a row.