Michelle Monaghan originally had a more substantial role in the film. When screening audiences reacted negatively to the long running time, her sub-plot was removed.
George Clooney suffered a spinal injury during a stunt. Due to the weight he gained for his role, the injury left him bedridden for a month and caused severe migraines, which prevented him from doing publicity for Ocean's Twelve. The injury was eventually corrected with surgery. Clooney has since called his weight gain "pretty stupid".
The scene in the front doorway of the Sloan Whiting law firm, next to the U.S. Capitol, is actually the real-life law firm Jones Day, located at 51 Louisiana Avenue, NW.
Harrison Ford was the original choice to play Bob Barnes, but turned it down. He later told Empire magazine that is one of the few movie career decisions that he has regretted.
In the days leading up to the Oscar nominations, the Academy announced that the film's screenplay was considered original, not adapted. Since it had been strongly advertised as adapted, many believed the film would not be nominated. It was nominated for Best Original Screenplay, but lost to Crash.
The trivia item below may give away important plot points.
When Hossein Hashimi is assassinated, an actor who strongly resembles former CIA director George Tenet is milling around in the background of the CIA operations room.