The win snapped a three-game Steeler losing streak.
Another key factor besides Parker: The Steelers (3-6) had no turnovers, while the Saints (6-3) had three, including one by Terrance Cooper in the last minute of the game on Pittsburgh's 25-yard line.
Parker carried the ball 22 times and big Ben Roethlisberger completed 17 of 28 for 273 yards and passed for a touchdown.
Hines Ward had five catches for 86 yards and a score.
Deuce McAllister scored twice, but had only 60 yards on 15 carries.