Triathlon star Sarah Crowley has held off a fierce New Zealand challenge to join Tim van Berkel as first-time Ironman Australia winners.

It is the first time since 2013 that two Australians have won the Port Macquarie race on the NSW north coast.

Crowley, the top name in Sunday's race, was pushed all the way by Rebecca Clarke and only beat her by one minute seven seconds.

By contrast, van Berkel pulled clear in the marathon to comfortably win by 11 minutes.

Crowley has finished third twice at the Hawaiian Ironman world championships and was the overwhelming favourite for the women's race.

But Clarke led after the 3.8km swim and they duelled throughout the 180km cycle, before Crowley held her off in the 42.2km marathon.

Crowley won in nine hours six minutes four seconds and compatriot Courtney Gilfillan took third in 9:30:48.

Crowley has struggled over the last couple of years with injury and the disruption of the COVID-19 pandemic.

Port Macquarie was an important step for her buildup to October's Hawaiian Ironman.

"That was one of the hardest races I've actually ever had to do to win, so full credit to Bec for being there all day and putting the pressure on," she said.

"It means a lot because I've had a rough couple of years. I haven't been able to get my form back to where it should be, and I think this is the start of something really good."

After feeling out of sorts midway through the bike, when he was about six minutes off the pace, van Berkel steadily regained ground and took the lead 16km into the run.

He powered away to win in 8:15:14, 11 minutes ahead of compatriot Josh Amberger, with New Zealand's Jack Moody third in 8:35:40.

"It feels good, especially as I'm turning 38 this year and I started to lose a few sponsors and a few people saying 'you're getting too old, you might need to retire'," said van Berkel, who is a top-10 finisher at Hawaii.

"A few mates have actually nicknamed me the journeyman so just good to stick it to them, there's still some fight left in this old dog."