If you are heading into Auckland City this weekend, plan for delays as thousands gather to see some of the world's top triathletes competing.

There will be road closures, parking restrictions and bus changes to cater for the Barfoot & Thompson World Triathlon series, which runs until Monday, Labour Day.

Daryl McIntosh from Auckland Transport said people coming into the city for the event or other attractions in the area should plan their journey and be aware of road closures.

Main roads affected in the CBD include Queen St, Albert St, Quay St, The Strand, Victoria St and Wellesley St.

Also, because of road closures for the race, a number of bus stops in the central city will be temporarily relocated.

Auckland Transport officials will be on hand to guide commuters to new stop locations.

People heading to the event can travel by bus, train or ferry.

Triathlon NZ chief executive Craig Waugh said it was an exciting time for the sport, which has attracted 160,000 people from all over the country in the past 12 months.

"From a recreational point of view, it's a good Kiwi sport to get into - people love to bike, run and swim. It's also got a clean, green vibe to it," Mr Waugh said.

About 3000 people are expected to compete in the triathlon series - including 750 New Zealanders.

"The sport is going crazy globally and we're riding that wave out here as well. It's very popular and it's the fastest-growing sport here at the moment," Mr Waugh said.

People are encouraged to arrive early for some of the best spots to watch the athletes: along Queen St, Shortland St, at the Queens Wharf grandstand and around The Cloud.