Clooney, who previously played the character in the infamous 1997 flick "Batman & Robin", admitted during an interview for The Hollywood Reporter's Awards Chatter podcast that when Affleck approached him for advice, he suggested he should walk away from the project.
"I actually did talk to him about it. I said, 'Don't do it'," the 58-year-old recalled. "It was only from my experience, which is, you know...".
The "Ocean's Eleven" star's stint in the role was widely panned by critics, and the film went on to become the lowest grossing movie in the entire "Batman" franchise.
However, Clooney, who also worked as a producer on Affleck's 2012 movie "Argo", confessed that he was impressed by the actor's performance in the films.
"He did great, though," the "Catch-22" star enthused.
Clooney went on to reflect on his experience in the movie, which also starred Chris O'Donnell and Arnold Schwarzenegger, and shared that the negative reception the film received encouraged him to give greater consideration to roles he's offered before accepting them.
"What I learned from that failure was, I had to rethink how I was working," he mused. "Because now I wasn't just an actor getting a role - I was being held responsible for the film itself."