"The Men Who Stare at Goats," directed by Grant Heslov, is being shown out of competition in Venice on Tuesday.
Clooney arrived in Venice by speedboat on Monday night, with Italian actress Elisabetta Canalis in tow. The two, who have been seen together recently, are expected to walk the red carpet Tuesday evening.
Clooney, who owns a villa on Lake Como and spends time in Italy, is a frequent guest at the festival.
The movie co-stars Ewan McGregor, Jeff Bridges and Kevin Spacey. It tells the story of a special U.S. army unit experimenting with paranormal powers in warfare.