Manning went 25-of-35 through the air for 306 yards, finding Hakeem Nicks on a pair of scoring strikes. But he also threw three interceptions, including one to Keith Brooking in the fourth quarter that helped the Giants stage a late comeback attempt.
Back-up quarterback Jon Kitna connected for a pair of fourth-quarter TD passes to help Dallas rally from a 38-20 deficit and pull to within six points with 40 seconds left.
The Giants (5-2) secured their fourth straight win when they recovered the ensuing onside kickoff attempt.
Nicks ended with nine grabs for 108 yards and Steve Smith hauled in nine receptions for 101 yards and a score, while Ahmad Bradshaw racked up 126 yards rushing on 24 carries for the Giants.
Kitna completed 16-of-33 passes for 187 yards for Dallas (1-5) after starting signal-caller Tony Romo left the game in the second quarter with a broken left collarbone.