According to Les Nouvelles Caledoniennes, several thousand people joined a march from the seat of government to the Congress building, organised by the group ReinfoCOVID.
The demonstrators are also against the so-called health pass introduced in France.
The rally comes just a day after the Congress unanimously voted to make vaccinations for adults mandatory by the end of the year.
There is no general penalty for those refusing to comply, but medical staff and port and airport workers will be fined US$1,750 if they refuse inoculation.
New Caledonia is COVID-19 free but only a third of the population has been vaccinated.
A Congress member Philippe Michel said being COVID-19 free gives the authorities an extraordinary opportunity and an immense responsibility that this situation can be maintained.
The government's spokesperson Yannick Slamet said the new obligation makes New Caledonia the fourth country to impose vaccination compulsion, after Tajikistan, Turkmenistan and the Vatican.
Photo source Les Nouvelles Caledoniennes