The Philadelphia Phillies' 5-4 victory over the Tampa Bay Rays, which ended at 1:47 a.m. Sunday, earned a 6.1 fast national rating and 13 share on Fox, the network said.
The previous low was an 8.0 in 2006 for Game 1 of the Cardinals-Tigers series.
The game averaged a 6.5/13 from 11 p.m.-midnight EDT, slid to 6.0/14 for the next hour, then rose to a 6.3/17 after 1 a.m.
The game drew a 28.2/49 in Philadelphia and a 21.6/44 in Tampa. With most of the game in prime time on the West Coast, some of the best ratings outside the home markets came there, including a 9.7/19 in Seattle and a 9.2/20 in San Francisco.
Through three games, the World Series is averaging a 7.7/14, down 23 percent from last year's 10.0/17 for Red Sox-Rockies.
The rating is the percentage watching a program among homes with televisions, and the share is the percentage tuned into the broadcast among those households with TVs on at the time.