Triathlon NZ chief executive Craig Waugh said it was a great way to promote the fastest growing sport in the country.
"It's the Rugby World Cup for triathlon. We're the fastest growing sport here in New Zealand - in terms of participation - and so to have it here is a good thing for the sport."
There are a number of race categories that will be going on during the day, so there will be many full and half-road closures in parts of the city centre, particularly downtown.
The advice to the public is to either travel early into town to avoid getting caught in traffic or avoid the city centre.
Auckland Transport spokeswoman Sharon Hunter said delays were expected so motorists needed to plan ahead.
"Journeys should be planned allowing plenty of extra time to arrive at destinations or motorists should consider alternative routes."
As well as the dozens of full and half-road closures, many parking restrictions will be in force.
All races start from Queens Wharf.
The Age Group triathlon race, from 7am to 11am, runs through parts of Parnell, Shore Rd and the waterfront.
The ParaTriathlon, from 9am to 11am, runs down the waterfront.
The Elite Women's Race is from 12pm to 2pm and runs through various parts of the CBD.
The last race, the highly popular Elite Men's Race, starts at 2.45pm and runs to 4.30pm, the route throughout the CBD.
A number of bus routes will be affected and several bus stops will be relocated and routes diverted.
Mr Waugh said another top international triathlon event - the World Series Final - will be held in Auckland, where it will finish.
He said that event, together with this weekend's triathlon, would help contribute to the Auckland economy, given that thousands of people were expected to head here for it next year.
"That was part of what we said, when we bid to bring the events here - that it would bring money into the economy. Here in Auckland but also for the country."
For more information and for bus services affected, visit: www.maxx.co.nz.
For parking options, go to www.aucklandtransport.govt.nz.