The Republican movement plans to take its message to Prince William when the British royal opens the Supreme Court during his New Zealand visit.
Labour Party MP Claire Curran and other members of the movement plan to protest outside the court on Lambton Quay in central Wellington on Monday.
The demonstration will draw attention to what the protesters see as the irony of the prince opening the new court, which was established to sever New Zealand's links with Britain's Privy Council.
Ms Curran says in no way is the protest anti-monarchy, but it is pointing out the need for New Zealand to be a republic.
She says while there is not overwhelming public support for a republic at the moment, she would like to see the issue debated publicly.
The protest will coincide with another organised by the Public Service Association over Ministry of Justice staff pay rates.