The post on his personal Instagram account read, "Terenzo was in an accident this afternoon in Kumeu. He is in the emergency department where his injuries are still being assessed."
International organisation Ironman Triathlon has responded with support for the triathlete, saying, "All of us at Ironman would like to extend our well-wishes to one of our own, Terenzo Bozzone, who was injured while cycling in New Zealand today.
"Our thoughts are with him and his family and we hope for a full and speedy recovery."
Fellow athletes have also sent good wishes, including cyclist Pedro Sanchez who wrote: "Sending my thoughts and prayers to an amazing athlete, friend and human being Terenzo Bozzone."
English triathlete Graham McKenzie said, "Sincerely hope Terenzo is ok. Wishing one of Triathlon's nicest guys a speedy recovery."
American triathlete Joe Maloy sent his thoughts and healing energy, and Olympian Nick Willis posted, "This is terrible. Hope Terenzo pulls through ok. Praying for you mate."
Ten-time Ironman Dave Carroll wrote, "Shocking news for the triathlon community. Thoughts are with this terrific Kiwi tri- athlete, hoping he makes a full and fast recovery.
"He was having an awesome year after finally wining Ironman NZ going just under 8 hours."
TriathlonWorld.com, Triathlon NZ, Ironman NZ 2017 champion Braden Currie and Australian triathlete Belinda Granger were among others who also sent thoughts and prayers to Bozzone and his family.
Emergency services were called to Waitakere Rd at 2.20pm on Tuesday.
The road was closed between Boord Cres and Hanham Rd and reopened at 6.30pm.
A police spokesperson said the serious crash unit is investigating and trying to find the driver.
"Police have spoken to a number of witnesses and we are following strong lines of enquiries in relation to the identity of the driver," they said.
Bozzone has won 37 international titles, which includes 23 Ironman 70.3 or half-Ironman distance triathlon titles.
He is married to Kelly Bozzone, and has a son called Cavalo.
