The singer, actress and French first lady was due to attend the event in order to promote her role in Woody Allen's romantic comedy Midnight In Paris.
"I was dreaming of going [to Cannes]... I regret it but I cannot go for personal reasons and for professional reasons, unfortunately," she told RTL Radio.
The announcement only served to further speculation that Bruni-Sarkozy is expecting her first child, rumours which she has refused to comment on to the press.
When questioned by the station whether the reports have anything to do with her decision to pull out of Cannes, she answered: "[My] lips are, in a sense, sealed."
Woody Allen previously revealed that he was "delighted by" Bruni-Sarkozy's performance in Midnight In Paris.
The 64th Cannes Film Festival runs between May 11 and May 22.
