A total of 91,032 people paid to go to the Bristol Motor Speedway in the state of Tennessee to watch the Atlanta Braves and Cincinnati Reds duel.
The previous record was 84,857 fans, set on 12 September 1954, when the Cleveland Guardians hosted the New York Yankees in their old stadium.
The game in Bristol started on Saturday, but was suspended in the first inning because of rain. The fans returned to the track on Sunday, in smaller numbers, to see the conclusion of the Braves' 4-2 victory.
The two home runs of the game - both by Eli White - were celebrated by a customised Corvette, which drove around the track after each of the shots.
Dubbed the Speedway Classic 2025, the historic game was part of a series of MLB regular season games played on a neutral field.
According to the New York Times, the event was widely criticized by fans for the poor view from various points in the stands and the lack of beer and food at the track.
The all-time attendance record for a baseball game in the United States still belongs to the pre-season friendly between the Los Angeles Dodgers and the Boston Red Sox, played on 29 March 2008 at the Los Angeles Memorial Coliseum. That game sold 115,300 tickets.