The "Thor" star was originally approached to help get the movie made as a behind-the-scenes talent, and he didn't hesitate to jump onboard as he was fascinated by the story, which focuses on a troubled black teen stuck between a life of crime and his estranged father's urban-cowboy subculture.
The film is based on the Greg Neri novel "Ghetto Cowboy", which was inspired by the Fletcher Street Urban Riding Club, based at an inner-city stables in Philadelphia, Pennsylvania, and urban African-American horseriding culture.
"I was asked to be a producer on the film before being an actor, and I read that script on a flight, and as soon as we landed, I said, 'We have to do this,' " Idris told U.S. breakfast show "Today".
"It's such a beautiful story, there's so much common truth, even though it's a story about stables and people we might not have known exist, but I really got touched by the story and signed on (as a producer) immediately."
Idris initially wanted nothing to do with becoming a castmember, but he later relented and took on the role of the protagonist's father - in spite of his allergies.
"I didn't want to play (any character or have) anything to do with it because I'm allergic to horses, so I was like, 'Someone else can have that, I'm good, but I want to make this film,' and eventually I got involved so I took some antihistamines," he smiled.
However, he made sure to make the most of the bandana, which made up part of his cowboy costume, to shield his health struggles from the camera.
"There's a lot of shots where I've got a mask over my mouth, and it does look cool, but it's to hide my runny nose!" he laughed.
"Concrete Cowboy", which co-stars "Stranger Things" actor Caleb McLaughlin, debuts on Netflix on Friday