Auckland City Missioner Dame Diane Robertson is to resign after 22 years in the job.
She would stay on to assist the mission through the busy Christmas period.
The charity provides health and social services to poor people in Auckland.
Dame Diane said she was unable to say what she will be doing next but hoped to continue to serve the community.
"It does feel a little bit like leaving home," she said.
"So I am doing it with some trepidation, and some excitement about moving on to further projects."
Dame Diane said she had been approached to take on other jobs, and was currently considering those offers.
The Mission Board's acting chair Bishop Jim White said Dame Diane had led the mission through a period of unprecedented growth.