SINN Féin's Jennifer McCann is to step down as an assembly member within the next few weeks.
The West Belfast representative, who has been an MLA since 2007, has agreed to take up a new role with health minister Michelle O'Neill.
Ms McCann's successor will be selected on December 1.
Ms McCann said she will act as a party adviser to the minister.
"My party colleague and Health Minister Michelle O'Neill is currently involved in the biggest transformation of the health service in more than seven decades," she said.
"That is a huge task and she requested additional support form the party to deliver this important transformation. The party agreed and I was honoured that I was asked to take up the role as a party adviser to the minister.
"It has been an honour and a privilege to be elected to represent the people of West Belfast in the Assembly since 2007 and to serve as a Junior Minister in the Executive.
"I am looking forward to the challenges of this new role and to assisting the deliver of this radical shake up of the health service to improve the health outcomes of people in West Belfast and across the North."
