The movie will also star French Oscar winner Marion Cotillard and Hollywood actors Owen Wilson and Rachel McAdams.
The title, release date and Bruni-Sarkozy's role are expected to be announced later this week.
Allen, one of America's most prolific film writers and directors, said last year that he would like to use the former supermodel in one of his films but at that time he did not have a story for her.
Bruni-Sarkozy, 42, who married French President Nicolas Sarkozy in 2008 in a whirlwind romance, appeared briefly on the big screen as herself in Robert Altman's 1994 fashion satire "Pret-a-Porter."
She is also a successful singer-songwriter with a string of albums and in the past had affairs with Eric Clapton and Mick Jagger.
Allen has made a movie almost every year since 1971, and he won an Oscar for his quirky 1977 film "Annie Hall" starring Diane Keaton.
(Reporting by Jill Serjeant; Editing by Bob Tourtellotte)
COPYRIGHT: (c) Reuters 2010. All rights reserved. Republication or redistribution of Reuters content, including by caching, framing or similar means, is expressly prohibited without the prior written consent of Reuters. Reuters and the Reuters sphere logo are registered trademarks and trademarks of the Reuters group of companies around the world.