Passers-by looked confused when the clock struck 1 and the group, spread out across the footpath in George St, held poses for five minutes.
Some were mid-stride, one was carrying a bike and one lay down on the pavement.
Co-organiser Guy Ryan said the event showed "unity to combat climate change" and was part of a nationwide effort as groups in Christchurch, Wellington, Hamilton and Auckland also took part.
Mr Ryan is also co-ordinator of the Dunedin branch of 350, an international movement dedicated to fighting climate change and raising awareness of environmental issues.
The number 350, as parts per million, is the scientifically-calculated safe level of carbon dioxide in the atmosphere.
At present CO2 parts sit at 387.
Other World Environment Day events in Dunedin:
• The Otago Polytechnic launched a booklet A Simple Pledge. Towards Sustainable Practice, available online and in a printed version, outlining the polytechnic's attempts to make its own organisation more sustainable through recycling, composting and the establishment of edible campus gardens.
It also explained its goal of teaching sustainability throughout the curriculum.
• The Dunedin City Council launched a workplace travel plan to encourage walking, cycling, carpooling and public transport.
The DCC event also featured people talking about sustainable living courses.
