In a court filing, Jack Schaap says he was suffering from stress and depression and was struggling with his mega church's financial problems when he took advantage of the then-16-year-old he was counseling.
Schaap will be sentenced later this month.
As part of his plea deal, he's hoping to get the mandatory minimum sentence of ten years.
A church spokesperson talked in August about the investigation and its impact on the church, which is one of the largest of its kind in the country.
"It was starting out to be a difficult decision, but when we found out the facts, we had no choice, we had to do what was right," said Terry Duff, chairman of the Board of Deacons. "It's broken our hearts. We loved that man, and we trusted that man."
Schaap, 54, has led the mega church's 15,000 regular members since 2001. Until his dismissal last summer, he was also the chancellor of Crown Point's Hyles-Anderson College.
"If he deserves to be punished, then that's the law, and he's got to be punished, but as far as the church and everything, it will go on. I don't think things will change," said Hyles-Anderson College student Matthew Martin.
"We honestly are going to do everything we can to make sure that this is taken care of and that this will never happen again," said Duff.