But Willett will have to overhaul Finnish leader Mikko Ilonen and hold off a determined challenge from home favourite Graeme McDowell to win the £265,000 first prize at Fota Island today.
Willett's previous ace earned him a V40 Cross Country from the tournament sponsors in the final round of the Volvo China Open at the end of April.
And although the 26-year-old did not win anything for his "slam dunk" effort on the seventh hole at Fota Island - a £65,000 BMW 640 Gran Coupe was on offer on the 13th - it sparked a brilliant round which left him one behind Ilonen on 11 under par.
"We had a perfect number, 168 yards with an 8-iron, but you never expect it to slam dunk," Willett said. "That was a bit of a bonus."
Fresh from finishing 45th on his US Open debut at Pinehurst last week, Willett had already birdied the fourth and added another at the eighth to reach the turn in 32. The former English Amateur champion's challenge was slowed by a run of four straight pars on the back nine, but he then birdied four of the last five holes to beat the previous record of 64 set by Ilonen on Thursday.
"We've been playing great for a long time but could not seem to get anything going on the greens," added Willett, whose sole Tour title came in the BMW International Open in 2012. "But holing a wedge yesterday for an eagle on the second and an eight iron today certainly helps.
"Coming from the US Open last week, it was a slightly different mentality, it was quite tricky to stop playing 20 feet away from the flags and on the first day we were too cautious."
McDowell's challenge for a first Irish Open title at the 13th attempt looked to be petering out after he bogeyed the eighth and ninth to reach the turn in 37.
But the former US Open champion gave himself a talking to on the 10th and his patience paid off with birdies on the 11th, 16th and 17th to card a 69 and lie two off the lead on 10 under.
"Walking down the 10th I had to have a chat with myself and stay patient, I only needed three birdies not six," said McDowell.
"It helps having been in this scenario before and it was nice to birdie two of the last three there and get myself back in this golf tournament.
"I really enjoyed the crowd interaction today, it's been a fun week. I'll try and give them what they want tomorrow, an Irish winner, but there's a lot of names on that leaderboard that will have some issues with that.
"It would be a kickstarter for my season. It would be a big boost in the world rankings and Ryder Cup rankings."
Ilonen remained on course to claim his fourth European Tour title with a wire-to-wire victory thanks to a birdie on the last to complete a round of 69. And the 34-year-old former British Amateur champion, who won at Open venue Hoylake in 2000, admitted his chances would be improved by partnering Willett rather than McDowell in front of the massive home crowds.
"It will help," said Ilonen, who lost a play-off to Sergio Garcia in the Qatar Masters in January. "Graeme will be in front of us, but it will be the same as today. I have been leading all the way and handling the pressure well so far.
"I was off here and there today, especially with a couple of drives in the beginning on the par fives. All in all, I felt pretty pleased with how I am placed."