The 32-year-old keeper is out of favour at the Bernabeu, and is keen to play first-team football ahead of the World Cup in Brazil next summer. Arsenal and Manchester City have been strongly linked with the World Cup winner, with Barcelona also thought to be keen.
The Catalan giants are on the lookout for a new keeper with Victor Valdes set to leave the Nou Camp at the end of the season.
But club president Sandro Rosell insists Barcelona will definitely not be trying to sign Real Madrid's Casillas.
"Casillas is the icon of Madrid," said Rosell. "Seeing him play for Barcelona would be like Real Madrid buying Xavi."
Both Arsenal and Manchester City are reportedly weighing up January bids for the Spain stopper, with the Premier League giants thought to be unsure over their current number ones.
Wojciech Szczesny has failed to inspire great confidence at the Emirates Stadium while Joe Hart remains prone to the odd high profile error that seemingly sets back him.
But Arsenal brought in Emiliano Viviano from Palermo on loan on transfer deadline day which means a summer move for Casillas could be more likely for the Gunners.
And despite the mistakes, Hart remains City and England's number one although they may revisit the situation at the end of the campaign.