The Giants (9-5-1) gave Jim Fassel a division title in his first season as an NFL head coach and are assured of hosting a first-round play-off game on 27 or 28 December.
The game hinged on Jason Sehorn scoring on a 35-yard interception return and the defense forcing six turnovers. The Redskins (7-7-1) are still alive in the wild card chase, but need at least a win next week in their regular-season finale against Philadelphia.
"I don't know if I've ever felt this good about a football team," Fassel said. "This was a very emotional win. No one expected us to be here. The Giants were down, now we're back up."
The performance was the highlight of a season that saw Fassel, a celebrated quarterback guru, lead a team that finished last under Dan Reeves in 1996 to an improbable title that began with defeats in three of their first four games.
In Saturday's other game, Pittsburgh rallied for a 24-21 overtime win over New England. The win left the Patriots short of a play-off berth, while the Steelers will claim their fourth AFC Central title if Jacksonville lose at Buffalo.
Kordell Stewart completed a pair of crucial passes in overtime to set up Norm Johnson's 31-yard field goal as the Steelers rallied past the Patriots.Reuse content