Johnson scored twice and gained 107 yards on 22 carries. Quarterback Trent Green was 22-of-35 passing for 235 yards, one touchdown and no interceptions, and Tony Gonzalez and Eddie Kennison combined for 10 catches for 130 yards for the Chiefs (5-3), who have won three of their last four games.
They have beaten the Raiders six straight times.
Gonzalez, who finished with five receptions for 70 yards, has caught a pass in 76 straight games.
Kerry Collins was 21-of-40 for 175 yards, two touchdowns and one interception for Oakland (3-5), which had a modest two-game winning streak snapped. Sebastian Janikowski booted three field goals for the Raiders. His Kansas City counterpart, Lawrence Tynes, kicked two.