In a statement titled ‘brand protection’, the club said sales of fake shirts can “impact directly on club revenues” and official club merchandise could be bought from the Owls Megastore or online store.
“Although we cannot prevent supporters from wearing counterfeit shirts away from Hillsborough, we do respectfully request that such products are not displayed inside the stadium,” the statement added.
The Owls begin their Championship campaign on Sunday at home to Plymouth (16:00 BST).