The pop star said her brother Frankie was told "God didn't love him" because he was homosexual and she thought "that's not cool".
She has now turned to the Kabbalah faith, which is an offshoot of Judaism, and said she thinks it's made her a better person.
In an interview with The Sunday Telegraph, the 21-year-old said: "Since then, my life has unfolded in a really beautiful way, and I think that it has a lot to do with the tools I've learned through Kabbalah, I really do."
Last year the 'problem' singer told the Metro her gay brother wasn't the only reason she lost her faith: "I was born Roman Catholic but I lost faith when the Pope decided to tell me everything I loved and believed in was wrong.
"[The Church] said SpongeBob SquarePants is gay and he's a sinner and he should burn in hell. And Harry Potter was a sin. And working women. I was like 'Enough! First the gays, then Spongebob and now Harry Potter? Get out my house!' I was not having it.
"And the working woman thing? It was a moment for me. I needed something else to believe in."
Ariana Grande has given her brother support in the past. Earlier this year she rejected criticism directed towards him on social media when he appeared on the American version of Big Brother.
Several homophobic comments were made against him.