Along with supporters, about 40 people marched from St Paul's Church, along lower Thames St and back to the church, singing songs, carrying placards and handing out pamphlets titled "A Call for Solidarity and Prayers" and Tuvaluan flags.
The sailors have been in the clutches of the pirates after being seized off the Horn of Africa in early April.
The pirates are demanding $US15 million ($NZ24 million) ransom and the Tuvalu Island nation has appealed to Australia for help to secure their release.
March organiser Silou Tevao said it was organised to raise awareness of the plight of their fellow countrymen.
"We also want prayers and help to free our boys. It's been three months and nothing has been done - we are looking for someone to step in and help," she said.
The island has a population of about 12,000 people.
Four Tuvaluan families live in Oamaru, and two families had come from Dunedin for the march.
The march came to an end at St Paul's Church, where prayers were held.
