The ad attacks Senate bill 25, which would require farm workers to be part of the United Farm Workers of America. But those in favor of the bill say the ad is misleading because it uses a person with an accent speaking against the bill.
The company behind the ad is Gerawan Farming of Fresno.
Officials say it's unfair to force farm workers to join unions and are calling on state law makers to strike down the legislation.
The bill is up for a vote in the assembly over the next four weeks.