Air New Zealand Hawke's Bay International Marathon's financial impact on the region is estimated to be about $3-4 million, Napier mayor Bill Dalton says.
Mr Dalton said the event was "absolutely amazing" and the positivity had lingered, with cafes and town streets bustling with people for the entire weekend.
Hawke's Bay's streets became visibly busier as people began flooding into the region ahead of Saturday morning's race.
Mr Dalton, who handed out medals at the finish line, said he noticed many were visitors to the region.
Marathon organisers confirmed about 75 per cent of the 8000 to 10,000 spectators came from out of town.
"This marathon is an example of what happens when you partner with strong agencies like Air New Zealand."
He said the airline had the "amazing" ability to bring people into the region and proved so by adding 17 extra flights to their schedule specially for the event. The mayor said the estimated financial impact lay between $3-4 million.
"But we mustn't lose sight of the fact that this was the inaugural race. There's already things [the organisers] are planning for next year."
While a feature of the event was the fine weather, Mr Dalton said the region was in desperate need of some rain now the event was over with. Hawke's Bay Tourism general manager Annie Dundas said the event had transformed what was usually a quiet weekend in May to an incredibly busy one.
"It's given May quite a boost."
Ms Dundas said there were not many options available for accommodation in Napier, and Hastings and Havelock North had filled up pretty quickly as well.
Many people chose to stay in private homes or bed and breakfasts, too.
She said a number of the people who had visited the region during the weekend were "star-struck" with the lifestyle, environment and produce on offer.
Ironman Oceania, who delivered the event, are sending out surveys to competitors to track some of the impact on the region, with questions about where people stayed and what they spent their money on, Ms Dundas said.
Ironman Oceania managing director Dave Beeche said the event had been a "real boom" for the region.
The date has already been set for next year's race, May 13, with many current features continuing as well as room being made for a couple of extras.
A sell-out this year deemed it a success and when asked if future ticket numbers would be increased, Mr Beeche said it was too early to confirm. But he did not rule it out and said organisers were anticipating future growth.
"Hawke's Bay just delivered a spectacular day."
Hastings mayor Lawrence Yule said the event would have been one of the biggest sporting ones the region had seen.
"It's been a stunning success."
Helping out at the halfway point and at the finish line, Mr Yule said he was stunned at the sheer volume of people.
"Most people will go away thinking Hawke's Bay is a pretty amazing place."
Hawke's Bay Chamber of Commerce chief executive officer Wayne Walford said the ramped-up traffic numbers were enough of an indicator to show how positive the event had been for the region.
He said the number of people who turned out was "just amazing" and all Bay businesses would have benefited in some way from it.
"It's been a fantastic weekend."