UEFA said an organised group of people impersonating stewards or officials might try to steal tickets at the Champions League final on Saturday.
European football's administrative body said Spanish police had seized "fake steward bibs, fake devices for the technical ticket check, as well as fake accreditations".
Several thousands of football fans are expected to travel to Madrid to watch Liverpool and Tottenham face off at the Wanda Metropolitano Stadium.
The stadium's capacity for the final is 63,500 seats of which 4,000 tickets were offered to general fans via UEFA's website. Each team was given an allocation of around 17,000 tickets. Around 23,500 tickets were allocated to "the local organising committee, UEFA and national associations, commercial partners and broadcasters, and to serve the corporate hospitality programme".
Supporters should "only show their tickets at the clearly marked check zones and not to individuals or small groups of people who could be wearing fake bibs and might approach them on the way to the stadium, outside of the official check zones,” UEFA wrote in a statement to Euronews.
On Friday UEFA warned that there were a high number of fake tickets in circulation.
They encouraged fans not to be "duped" and said there were no fan tickets being distributed via third-party agencies.
Tickets for the event cost between €70 and €600 when purchased through UEFA's official website but tickets were resold online for thousands of euros.
Madrid's municipal police tweeted that the Security Support Units arrested someone selling fake tickets that were of "very good quality."
The national police said the two-ticket scam was worth €8,400.
"Reselling tickets is a bad business that is often expensive and the offers can be false," the Spanish national police tweeted.
The final game takes place on Saturday at 9 pm CET.