In a tweet, the beer company announced that if Mexico beats Brazil and advances to the quarterfinals that it will help pay for customers' beer.
The tweet, written on charred parchment in a Medieval style as part of its King John Barley and Dilly Dilly gimmick, says "such a great victory shall be celebrated by him helping ye pay for thy celebratory Bud Lights," which appears to mean free beer.
The "curse of the fifth game" refers to Mexico not being able to advance past the fifth game in the World Cup since at least 1994.
Mexico faces Brazil in the round of 16 at 7 a.m. Monday.
If Mexico does break the curse, Bud Light said it will then provide further details on how to get the free beer.