Collins was taking part in ChildFund Water Run to raise funds to support local communities in the Pacific at 9am in Auckland’s Britomart when he collapsed.
Emergency services immediately responded with CPR and defibrillators to treat the MP and continued working on him for an hour.
An organiser for the event confirmed he had died at the scene.
Collins, 49, is survived by his wife Fia and two daughters.
He holds the Samoan ali’i chief title of Fa’anana from the village of Satufia, Satupaitea in Savaii.
Raised in South Auckland, he has always been a strong advocate for the area and the young people there.
A proud Samoan, Collins has always been involved in the Samoan and Pasifika community - particularly as an advocate for Pasifika youth.
Collins was elected to the Ōtara-Papatoetoe Local Board in 2013 and became its chairperson.
Three years later he was elected to the Auckland Council as one of two councillors for the Manukau ward.
At the 2022 local body elections, he stood for the mayoralty as an independent with the backing of the Labour Party and outgoing Mayor Phil Goff, where he was the runner-up to Wayne Brown.
He was elected to Parliament as a Green Party MP at the 2023 election.
MPs could be seen leaving select committee rooms in Parliament House after an unexpected adjournment apparently triggered by Collins’ death.
Some MPs could be seen crying as they headed for Parliament’s black and white tiles.
Green Party co-leaders James Shaw and Marama Davidson released a statement on Collins’ death, saying they were "absolutely devastated".
"A beautiful family has lost a dedicated father, husband, and community leader," the co-leaders said.
They sent their thoughts to Collins’ wife and young daughters.
"Aotearoa and the Green Party have lost one of the kindest, most dedicated champions of fairness and equality," they said.
Prime Minister Christopher Luxon also offered his condolences.
"I am truly shocked and saddened at the news of Efeso Collins’ sudden death," Luxon said.
"Efeso was a good man, always friendly and kind, and a true champion and advocate for his Samoan and South Auckland communities.
"Our thoughts and deepest sympathies go to his family, his community and colleagues."
Collins ‘happy, jovial’ before collapse
A representative for the event said Collins was "happy and jovial" in the moment before he collapsed.
People working at the event "jumped into action quickly" and started performing CPR on him immediately before the defibrillator was brought out.
"Everyone’s just waiting here, you know, praying for the best outcome for him at the moment," the representative said.
"We are obviously very upset and shocked."
An eyewitness said the incident happened a few minutes after the race winner was announced.
"They’d just announced the winner and everyone was standing around - then there was a scream. I turned around and he’s collapsed to the ground."
The outdoor event was attended by a number of high-profile Aucklanders including Dave Letele, The Hits host Matty McLean and Seven Sharp anchor Hilary Barry.
A witness said as emergency services arrived, many of the participants and event staff became emotional.
"There were lots of tears and everyone was hugging each other."
He was taking part in a water run race in Te Komititanga Square outside Commercial Bay to raise awareness and money for clean drinking water to children in the Pacific Contestants raced each other around a course carrying two filled buckets of water, with the person with the most water deemed the champion.
