Rev. Juan Demetrius McFarland of Shiloh Missionary Baptist Church in Montgomery confirmed to NBC affiliate WSFA that he made the admissions in a series of sermons that began in September.
Deacon Nathan Williams said McFarland was removed as leader on Oct. 5.
"He concealed from the church that he had knowingly engaged in adultery in the church building with female members of Shiloh Missionary Baptist Church while knowingly having AIDS," Williams said.
McFarland, who has been pastor for 21 years, could not be reached for comment on Thursday.
Montgomery Police Sgt. Denise Barnes said he is not under investigation because no one has made a complaint against McFarland. She said that in Alabama, spreading a sexually transmitted disease is a low-level misdemeanor.
The church has hired a lawyer.
"Our moves are going to come directly from counsel. We want peace and we want to do things right, legally," the deacon told WSFA. "We are not looking to hurt him. We are looking to get the church back."