Hundreds of supporters gathered at Selhurst Park to protest UEFA's decision, which was made due to the club's owner, John Textor, also holding a stake in Lyon, another team that qualified for the Europa League.
Textor has agreed to sell his share to Woody Johnson, but the deal has not been finalized yet.
The fans believe that Palace should have been allowed to participate in the Europa League, as they had qualified for it.
They pointed out that the team had won a cup and should have been given a spot in the competition without any issues.
One fan, Nick Philpot, said, "It's an injustice, just because of a couple of administrative errors. We qualified for it, and we should have been allowed to participate."
