Sanitarium spokesman Pete Davis said about 1000 children ranging in age from 7 to 15 travelled from across Otago to take part.
The children swam, rode and ran to the finish line as families and friends cheered them on.
The aim of the day was all about participation, Davis said.
No times were kept or winners credited. Instead everyone who crossed the finish line was given a medal.
With music in the air and positive encouragement from spectators, the mood was upbeat and cheerful.
Davis thanked the hundreds of volunteers who had helped make the event run smoothly.
"We couldn’t do it without the entire support of the community, so having volunteers is incredible," he said.
Thornbury said her journey into sports started by participating at similar events such as the TRYathlon, and she hoped young children would be inspired to think about becoming triathletes.
"We need some up-and-coming people."
Staufenberg said the event was about supporting the next generation of athletes "to be able to give tri a go, and hopefully quite a few of them stick to it".
"Take the opportunity."
As the event began, Dunedin Mayor Jules Radich thanked all the parents who had got up early on a Sunday morning to bring their children to compete.
"I’m also very proud of the kids here ... going to compete.
The Sanitarium Weet-Bix Kids TRYathlon series has been running since 1992 as an event designed to encourage children to stay active and healthy through a programme of participation.
Over the years more than 475,000 children aged from 6 to 15 have taken part.
