"Jonah Lomu was a hero to so many New Zealanders, young and old. He was a great role model and a doting father so we appreciated having him support UNICEF's work. We are very sad to hear news that he has died at such a young age. UNICEF NZ conveys its sincere condolences to Jonah's children, his wife, Nadene, and family at this sad time," said UNICEF NZ executive director Vivien Maidaborn.
Jonah became a UNICEF Ambassador four years ago and said at the time, "There are so many children around the world who are disadvantaged from the time they are born. As a dad myself, I want to help change those kids' lives and becoming an ambassador for UNICEF NZ is the best way for me to do that."
In 2012, Jonah took part in living on no more than $2.25 a day as part of an initiative of the Global Poverty Project, an education and campaigning organisation whose mission is to increase the number and effectiveness of people taking action against extreme poverty.
He was among a list of celebrities _ including Frank Bunce and MasterChef's Nadia Lim _ planning to Live Below the Poverty Line.
It was in 2011 that Lomu became an ambassador for children's charity Unicef New Zealand.
Lomu joined other prominent Kiwi who support the charity, including singer Hayley Westenra and a broadcaster, Mike McRoberts, as well as global sports stars such as tennis ace Novak Djokovic and Formula 1 driver Fernando Alonso.
Lomu, who was receiving dialysis after his transplanted kidney failed, said becoming an ambassador was the best way for him to help change kids' lives.
"My kids mean the world to me and I'm doing everything I can to give them the best start in life, but there are so many children around the world disadvantaged from the time they are born,'' he said.
"It is an amazing charity doing so much in New Zealand and globally to make a difference for children I'm so proud to call myself an ambassador.''
The Fight for Life in 2011 saw Lomu withdraw from the boxing ring, but he starred as the ambassador and helped raise $166,000 to help education hundreds of men about the need to get tested for prostate cancer.
Prostate Cancer Foundation chief executive Keith Beck said they had been overwhelmed with the amount of funds raised: "It's been a marvellous event for us and we're very please to have been involved.''
Mr Beck said the main aim was to raise better awareness about the need for men to visit their GP and get their blood tested.
"When you have someone like Wendell [Sailor] and Jonah Lomu looking down the camera and saying: 'Guys, get tested', then that's something.''