Prime Minister John Key will lead a delegation to Rarotonga to celebrate the Cook Islands' 50th anniversary of self-government in free association with New Zealand.
Opposition leaders and MPs will be there as well.
"Fifty years ago, New Zealand and the Cook Islands entered into a unique bilateral relationship," Mr Key said.
"We welcome the opportunity to celebrate that."
Mr Key will meet Cook Islands Prime Minister Henry Puna and take part in the official Constitution Day ceremony.
The delegation leaves on August 4 and returns on August 5.