Mansfield officially reported an allegation of racist abuse against captain Krystian Pearce to the Nottinghamshire Police, as well as the Football Association.
The incident happened on July 24 in a friendly between the two sides, with Mansfield boss David Flitcroft admitting that he felt the need to remove Pearce from the field after something had made him 'visibly upset'.
However, Wednesday have denied the allegations in a statement, saying: "Sheffield Wednesday are aware of the very serious allegations made following the pre-season friendly with Mansfield Town on Tuesday, July 24.
"The club vehemently refutes any form of racist abuse on our part and will vigorously defend itself should the need arise."
The FA has confirmed that it received a report of racism and is currently investigating.