Sam Rader, who, along with his wife Nia have more than 360,000 subscribers on YouTube, said the reports he had joined the site were true.
Ashley Madison matches married people to allow them to have affairs.
The email addresses and other details of members were put on the internet in a massive hack by a group unhappy at the moral nature of the website.
Sam Rader admitted that he joined the website two years ago before he joined YouTube.
In a video he said his church had been informed that he was a member.
"This has been brought to my wife's attention," he said, "she has forgiven me".
He added: "I have sought forgiveness to God, and he has forgiven me, so I have been completely cleansed of this sin.
"Also I need to be clear that I have never met with a single person face to face through that website and that I never had an affair with anybody ever, while I've been with Nia.
"Some of you are questioning my faith and me being a Christian and doing this and I guess what some people don't understand is that we're all broken, even Christians.
"We come to God as broken people and he has sent Jesus on the cross to save us from those sins."
He added that the issue was "completely resolved" within his family and church and that he would not speak of the situation again.
He said it was a "stupid thing" and that we were "sinful by nature".
It was "why we need a saviour", he said.