Lentz made the comments in an interview with US Weekly Magazine which touched on new book, "Own The Moment", as well as topics such as faith, pre-marital sex and relationships.
The magazine, which described Bieber and the church leader as 'BFFs' (best friends forever) , asked Lentz if his advice and sermons has caused the singer to change in the past couple of months.
He replied: "I don't think my teaching or my preaching has made even remotely as big of an impact as his own desire and passion and love for Jesus.
"That's how it should work. The primary change agent in somebody's life, it shouldn't be a person. It shouldn't be a preacher. It should be God.
"I think all his changes are a credit to him and him allowing God to continue to use him. Nobody gets credit for that."
Lentz added that Bieber has "worked really hard" to be the best version of himself and he was proud of him for his progress.
After Bieber was pictured going to church earlier this year, people spoke of his "rededication" to the Christian faith.
However, Lentz said there has not been a rededication.
He told the magazine: "What the world sees is a rededication and I don't think...that's not fair, that's not true.
"He's always been on a journey like we all are. To me this is just natural progression of somebody who is dedicated, and he's very dedicated."