Wolves striker Hwang Hee-chan was the target of "discriminatory abuse" during a friendly against Portuguese side Farense.
The Premier League club have called for an investigation from UEFA over the incident.
The South Korean striker was subjected to abuse from the home supporters in Portugal.
"We are very disappointed to report that one of our players was the target of discriminatory abuse from opposition fans during this evening's game with SC Farense," read the statement from Wolves.
"We will be reporting the incident to UEFA and asking our opponent and relevant authorities to investigate. We are offering our full support to the player involved.
"Racism in any form is completely unacceptable and should never be left unchallenged."
