The Eagles' defense kept the defending Super Bowl champions out of the end zone and came up with two big fourth-down stops in the fourth quarter.
Philadelphia will play at Arizona next week for the NFC championship and a trip to the Super Bowl.
McNabb ran 1 yard for a touchdown in the first quarter and hit Brent Celek on a 1-yard scoring pass in the fourth. McNabb completed 22-of-40 passes for 217 yards with two interceptions.
David Akers kicked field goals of 25, 35 and 20 yards for the Eagles.
New York quarterback Eli Manning connected on less than half of his passes, 13-of-27 for 158 yards, and was picked off twice.
The Giants got their points on three John Carney field goals and a safety. Carney also missed two field goal attempts.