After spotting Seattle a 7-0 first quarter lead, Philadelphia scored 26 unanswered points, with its defense yielding just 10 first downs and 233 total yards.
Its third straight win set up a battle with the NFC East-leading New York Giants next Sunday.
McNabb completed 28-of-43 passes, with one interception. His scoring passes, both in the second quarter, went to wide receiver Reggie Brown and offensive tackle Todd Herremans on a one-yard tackle-eligible play 40 seconds before halftime.
Eagles' running back Brian Westbrook gained 96 all-purpose yards (61 rushing, 35 receiving), tight end Brent Celek added 131 yards on six catches, and David Akers kicked four field goals.
The injury-riddled Seahawks were without five starters -- including quarterback Matt Hasselbeck -- in the fourth loss in their last five games.
Seneca Wallace, subbing for Hasselbeck, went 12-of-28 for 167 yards and a 90-yard first touchdown to Koren Robinson.