Pastor James McConnell, who once counted Iris Robinson among his flock, has cancer.
The senior figure at the Metropolitan Tabernacle on the Shore Road in Belfast said: "Recently I was diagnosed with prostate cancer and I am undergoing chemotherapy treatment."
The 75-year-old added: "I keep my congregation fully informed because I want other people with cancer to see how I am dealing with it. I hope that this will give them encouragement, rather than taking to their beds and pulling the curtains.
"I am not afraid of death. It is all part of God's plan for me and everybody else."
Pastor McConnell's congregation has included politicians like Peter and Iris Robinson, Finance Minister Sammy Wilson, and leading figures from soccer and rugby.