Bradley Cooper has opened up this week about struggling with substance addiction before his big break on 'The Hangover'.

Speaking on the Smartless podcast, hosted by Jason Bateman, Sean Hayes and Will Arnett, the 47-year-old delved into his life in his twenties and how Arnett helped him through his cocaine addiction.

Cooper shared the same apartment building with Arnett while they were still fledgling actors and his friendships with Hayes and Bateman goes back over twenty years.

On the podcast, Cooper told a story of a night out with Arnett and some comedians where he didn't come across very well, despite his recollections.

"Will was like, 'Hey man, do you remember we had dinner the other night? How do you think that went?' I was like, 'I remember being at the dinner thinking I was so funny. I thought these two guys who were my heroes thought that I was so funny.'" Cooper recalled. "Will's like, 'You were a real asshole, man. You were a real asshole.'"

David Boreanaz, Bradley Cooper and Will Arnett in 2005 (Image via Getty)

That same day, Arnett noticed that it was 4PM and Cooper still hadn't let his dogs outside to go to the bathroom.

"That was the first time I ever realized I had a problem with drugs and alcohol," said Cooper. "It was Will saying that to me, I'll never forget it... It changed my entire life."

"I was so lost and I was addicted to cocaine, that was the other thing," the actor continued. "I severed my Achilles tendon right after I got fired-slash-quit 'Alias'."

"Will took that risk of having that hard conversation with me in, like, July of 2000 and that put me on a path of deciding to change my life. It truly was Will Arnett. He is the reason."

Arnett, who struggled with his own addiction issues, got emotional during the conversation. He said, "It has been awesome seeing you in this place and seeing you comfortable, nothing has made me happier."

Cooper also said that therapy and fatherhood helped him become a better person. He shares a 5-year-old daughter with ex Irina Shayk. "Fatherhood…everything changed," he said. "Every single thing is absolutely shaded by or brought out in glorious colors by the fact that I get to be a father to a wonderful human being. It’s just the absolute greatest thing."

You can listen to the full episode of 'Smartless' here.