The rocker/actor put his Hollywood career on the backburner while concentrating on his band 30 Seconds to Mars, and he recently revealed he planned to turn down the part of an HIV-positive cross-dresser.
However, Leto now admits he signed up for the role after learning he would be working with MCConaughey.
Speaking at Canada's Toronto International Film Festival, Leto explains, "It's been five years (since my last film), but who's counting? How can you miss me if I never leave, right? It was an amazing role, it was an amazing script... but I have to say, Matthew MCConaughey is doing something spectacular with his life (and) his career. I wanted to be a part of that.
"He's doing the most incredibly inspiring work and I said, 'If he's willing to walk down this path, I have to get in the ring with him.' That's someone I have to dance with, am I right?"