Foxx portrays the real-life Walter McMillian in Just Mercy, who has his wrongly convicted death row sentence overturned by lawyer Bryan Stevenson who started the Equal Justice Initiative.
Michael B. Jordan portrays Stevenson in Just Mercy with Larson as Stevenson's partner Eve Ansley.
"I think it's a story of humanity and something that we can all rally around," the actor said on Wednesday before he explained how the film relates to his own personal life.
"I went through this with my own father. He was an educator for 25 years, they put him in jail for $25 worth of illegal substances for seven years," Foxx said. "So I was familiar with having that type of sunkenness in a sense. So when I put that skin on of Walter McMillian it was easy for me to get to it.
Foxx and Larson invited Stevenson onstage who was watching the show from the audience.
"I'm just so excited that people will now get to know a lot of the people I've been working with who sometimes feel like no one cares, no one sees them. But they become invisible because they've been thrown away in these spaces. We've got thousands of innocent people in our jails and prisons" Stevenson said.
"I hope this film inspires people to want to do something about that and change our system," he continued.
Just Mercy, based on Stevenson's book Just Mercy: A Story of Justice and Redemption and directed by Daniel Cretton, arrives in selected theaters Christmas Day and then opens nationwide on Jan. 10.