The Australian actor, who plays a cage fighter and appears alongside Tom Hardy in the action movie, said that he ignored medical advice because the role fascinated him.
Edgerton told The Age: "You take a few punches in the head, but that was kind of fun. I was actually advised by a doctor here in Sydney that it probably wouldn't be a good idea to do the movie. But I wasn't going to let that stop me. I'm not smart enough to take advice like that."
He revealed that Warrior's director Gavin O'Connor hired him and Hardy because they don't "have a lot of movie star baggage", but said that they worked very hard to do their roles justice.
Edgerton also admitted that he got slightly competitive with Hardy - who plays his brother in the film - when they bulked up for Warrior.
He said: "I was about as big as I could get with the amount of food I was shoving in to me, and the weight I was losing. I wasn't going to get any bigger. And he just looks huge."
Edgerton added that Hardy would "walk in and do a fight and it would take a day to shoot", compared to him taking "two weeks".
Describing himself as "pretty guarded" about his life, Edgerton admitted that his life has "changed in the past decade and the career "doors have opened wider".
"I'm thankful of it," he said, "and I realise that I'm swimming around exactly where I wanted to be ten years ago and I've got those opportunities now."
> Tom Hardy: 'Warrior proved I'm not that manly'
Watch Tom Hardy and Joel Edgerton talking about Warrior with Digital Spy below: