Australian triathlete Kylie Simpson continues to build an impressive resume, winning the Ironman Asia-Pacific title for the second time and setting a course record.

New Zealander Braden Currie also broke the men's course record to win his third title at Cairns.

Adding more lustre to Simpson's win, it came after she backed up from winning last month's Ironman Australia title in Port Macquarie.

Simpson clocked eight hours 40 minutes 53 seconds for the 3.8km swim, 180km cycle and 42.2km run event, beating compatriot Radka Kahlefeldt by a whopping 18 minutes.

Penny Slater made it an all-Australian podium as defending champion Sarah Crowley faded to fourth after leading at the start of the marathon.

Simpson also won Cairns two years ago and this time sliced eight minutes off the old course record, set by New Zealander Teresa Adam four years ago.

"I just got on the bike and just put my head down and got into a rhythm and just took as much time out of the girls as I could," said Simpson, who was also third at Cairna last year.

"I knew I was chipping into them, I didn't know that I was on course for the record so that's a little bonus.

"Coming into T2 (bike-run transition) and all of us in that change tent together, that was a good moment to realise how close we were and I knew that they (Crowley and Kahlefeldt) can both run well, they're both champions and I knew what I was up against.

"Sarah's won here multiple times, she's been on the podium at Kona, Radka's been to the Olympics so I knew that I couldn't let them get away so I had to put as much time into them as I could."

In the men's race, Currie clocked 7:50:11 to take two minutes off the course record set last year by Australian star Max Neumann.

Unlike Simpson, who was more than 12 minutes down after the swim, Currie was among the leaders throughout the race.

He powered clear in the marathon to finish 10 minutes ahead of Steve McKenna, with fellow Australian Tim Van Berkel nearly four minutes furth back in fourth.