Black smoke billowed out of the stadium's right smokestack for several minutes while the game played on. A fire ladder extended from a truck parked behind the stadium and the flames were extinguished.
According to the San Francisco Chronicle, a message posted on the stadium's scoreboard said that a "malfunction" caused the fire and that there was no threat posed to fans.
In a light-hearted moment, stadium operators played Billy Joel's "We Didn't Start The Fire" as firefighters extinguished the blaze.
Great American Ballpark will host the 2015 All-Star game July 14.