Wearing a floor-length olive green satin gown, she walked the “green” carpet where she spoke to media on Tuesday, praising it for helping amplify the solutions needed to fight climate change.
The Earthshot Prize was created by Britain's Prince William to fund projects that aim to save the planet.
Ardern became a trustee of its board shortly before leaving leaving office earlier this year.
She spoke to media outlet Bloomberg about the need for quick action in the battle against climate change.
“We see there’s a growing number of individuals, private equity and so on, who are looking to climate investment.
“We need to be making sure we have the solutions now and that we’re investing in those solutions now. We can’t afford to wait.”
The Earthshot Prize awards £1 million ($NZ1.23 million) to each of five green innovators working on projects including a cleaner lithium-ion battery and ocean conservation.
"The light of optimism is burning bright in our Earthshot finalists," Prince William said on Tuesday.
The five winners includes one from Hong Kong who is working on building cleaner, recyclable lithium-ion batteries that are used in electric cars, and another that tightens marine enforcement to end illegal fishing and support ocean conservation.
Representing six continents and chosen from over 1300 nominees, the 15 finalists' projects ranged from a scheme to plant, grow and digitally track trees in Liberia to a less carbon-intensive method of treating industrial wastewater.
This year marks the first time that the finalists are attending the awards ceremony in person, Kensington Palace said.
William, who became heir to the British throne after Queen Elizabeth II died in September last year, set up the prize in 2020.
Its name is a nod to former US President John F. Kennedy's ambitious "moonshot" project and goal for the 1969 moon landings.
During the four-day trip to Singapore, one of Asia's greenest cities, William will meet Singaporeans and "learn about how local organisations are working to protect and restore our planet - from tackling the illegal wildlife trade and protecting the rainforest to incubating and scaling cutting edge innovations," Kensington Palace said.
This is William's first trip to Singapore since 2012, when he visited with his wife Catherine, the Princess of Wales.
