Brian Thompson has been co-opted to Mid and East Antrim Borough Council to replace Colin Crawford MLA, who replaced Robin Swann in the Assembly.
Cllr Thompson will represent the Ballymena District Electoral Area (DEA) for the Ulster Unionist Party (UUP).
The Chief Electoral Officer for Northern Ireland, Dr David Marshall, confirmed the change on Tuesday.
The UUP are yet to release a statement relating to the change.
