Tūpuna Maunga o Tāmaki Makaurau Authority is set to begin work banning cars, motorbikes and scooters from the summit of One Tree Hill (Maungakiekie) on March 26.
The authority plans to reconfigure the entrance to the summit road and install an automatic gate.
Installation is expected to take four to six weeks, during which vehicles, cyclists and pedestrians will continue to have access to the summit.
The official closure date will determined based on the progression of construction work and will be announced one week prior.
Following the closure, people with mobility issues will be able to call the Auckland Council call centre and obtain an access code for the gate.
One Tree Hill is the third mountain to be closed to traffic, following the closure of Mt Eden in 2016 and Mt Victoria on March 1.
It's part of a plan announced by the Tūpuna Maunga Authority in November 2016 to remove vehicles from five of Auckland's mountains.
"Since the changes at Maungawhau [Mt Eden] we have had consistent feedback from visitors that the maunga is a vastly more peaceful and safer place to be without cars driving up and over it," said Tūpuna Maunga Authority chair Paul Majurey.
"What is really pleasing is the increasing number of people who are understanding and connecting with the preservation of these taonga, and the work to bring their natural qualities and cultural history to the fore."
Work is now also underway to make the summit of Mt Roskill (Pukewīwī/Puketāpapa) car-free.