The "Sunday Night Football" matchup between the last two Super Bowl champions drew an 11.8 overnight rating and 18 share. Game 4 of the World Series had a 10.4/16.
The Saints beat the Steelers 20-10 on NBC. The Giants defeated the Rangers 4-0 on Fox.
NBC had skipped airing a Sunday night game during the World Series the first four years of its current NFL contract. NBC said Monday this was the first time an NFL game outrated the World Series.
Ratings represent the percentage of all homes with TVs tuned into a program. Shares represent the percentage of all homes with TVs in use at the time. Overnight ratings measure the country's largest markets.
Game 3 earned the second-lowest television rating for a World Series game.
The Texas Rangers' 4-2 win over the San Francisco Giants on Saturday night on Fox drew a 6.7 rating and 13 share, beating only the 6.1 for Game 3 of the 2008 Phillies-Rays series. That game was delayed 91 minutes because of rain and didn't start until after 10 p.m. on the East Coast.
The rating was down 26 percent from the 9.1 for Game 3 of last season's Yankees-Phillies World Series.
This year's series averaged an 8.1 through three games, up 5 percent from the record low of the 2008 World Series.
Saturday's game began at 7 p.m. EDT, the earliest World Series start since 1987. Baseball and network officials had for years resisted earlier start times despite concerns about losing younger viewers, saying the later the game, the higher the rating - and the greater the revenue. To help offset potential revenue losses from the earlier Game 3 start, sponsor Chevrolet committed to increased advertising.
Baseball Commissioner Bud Selig wouldn't assess the ratings.
"Let me study things," he said before Game 4.
For the first time during this World Series, Cablevision's more than 3 million New York-area subscribers were able to watch the game after the company settled its dispute with Fox.
The rating is the percentage watching a program among homes with TVs. The share is the percentage tuned into the broadcast among those households with TVs on at the time.
Fox is a unit of News Corp.