The amount of the fine was not disclosed.
Sheffield was suspended for the incident, but had that suspension reduced to two games.
Having already argued a strike call made by Gibson during a game against Cleveland May 31, Sheffield broke his bat on a ground ball. He tossed the remains of the bat to the ground in Gibson's direction and was promptly ejected.
Sheffield, who had run a short distance toward first base, turned and headed toward Gibson. The Tigers' designated hitter-outfielder had to be restrained by his manager and teammates.
Sheffield later said baseball's umpiring system was, "corrupt."
"Our highly professional umpires protect the integrity of the game on the field," Commissioner Bud Selig said in announcing the fine. "Attacks on their professionalism and character will not be tolerated."