An official was on hand to certify the achievement after it reached the 10-minute mark, which was the original idea of Angels marketing associate John Rozak.
It shattered the existing mark of 250 people wearing costume masks at the same gathering.
There was a countdown in the crowd as the 10-minute barrier passed and masks came off thousands of heads. It occurred as Howard Kendrick was smacking his second double of the night, giving the Angels a 6-1 lead over the White Sox.
It became official at the end of the inning. Angels fans had, indeed, set the record.
Lyle Spencer is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.