Her upcoming A&E docu-series, Leah Remini: Scientology and the Aftermath takes an in-depth look at the lives of other former members of the Church of Scientology, which Remini famously left in 2013.
"It's bold and brave and amazing," DeGeneres said about the series' first episode.
"That's what made me want to do the series," Remini said. "A&E is very brave to do it. And the people who are speaking are very brave to do it because the repercussions to speaking out [are severe]. And that's why I said, 'OK, I can't sit back.'"
Remini has been vocal about the inner workings of the church, and released a book in 2015 about her 30 years in Scientology.
"I was watching high executives, former executives of the church leaving and speaking out about abuses and things that they've experienced while working for the church, and I saw how the church reacted," Remini told DeGeneres. "I felt I had a responsibility to say, 'I'm not going to allow you to bully these people who were very brave to come out and tell their stories.' And that from executives. But there are average parishioners like me who leave and speak out about what they've experienced. They lose their family. The church goes after their family to shun their family. I'm very lucky that didn't happen to me. My family chose me."