Mr Abbott completed the event, which involves a 3.8km swim, a 180km bike ride and a 42km run in just under 14 hours, shortly before 9pm on Sunday.
Fitness fanatic Mr Abbott - a first-time Ironman competitor - finished in 1169th spot in the race, three hours before the cut-off time.
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The 53-year-old, who had been training for 10 hours each week in the lead-up to the event, admitted he struggled during the water leg of the course.
"That, for me, was a really hard leg because it was the biggest swim I've ever done in my life," he told reporters.
Mr Abbott's devotion to exercise has led to criticism from some on both sides of politics, with suggestions he should spend less time working out, and more time developing policy.
Ironman effort 'admirable'
Health Minister Nicola Roxon said Mr Abbott's Ironman effort was "admirable" and set a healthy example for Australians.
But, she argued, politics is a contest of ideas and the opposition leader has been neglecting policy development.
"It's a fair question to say: Does that amount of time [spent exercising] actually have an impact on the lack of policy development that we're seeing from the opposition," Ms Roxon told ABC TV.
"Ultimately, we don't have an issue with what Mr Abbott chooses to do. What we do have an issue with is that so far he doesn't have a health policy or many other policies."
But opposition regional development, infrastructure and water spokesman Barnaby Joyce says exercise was Mr Abbott's way of relieving pressure.
"He sends a message back to the Australian people that it doesn't matter what age you are, if you stay active you give yourself the best chance of having a healthy lifestyle," Senator Joyce said.
"What Tony's doing is immense. I'm awe-inspired that he actually has the capacity to do it."
