The world number five Scott showed great composure on a windy day to shoot five-under 67 for a 17-under total of 271 and clinch his first tournament win of the year after a frustrating season of near-misses.
"To have it out with a world-class player and come out on top is very satisfying," the 32-year-old Scott said, donning the winner's 'Gold Jacket', a nod to the more salubrious green-coloured one handed to victors at Augusta.
"Probably it's the only week of the year... where I've put four really solid rounds together and the result shows, so I'm really, really happy with what I was able to do this week and especially today."
With daylight separating Poulter and Scott from the rest of the field, the final round was reduced to a matchplay battle, and the Australian raised the pressure on his playing partner with a pair of birdies in his opening holes to snatch the lead.
But any hopes of a repeat of Saturday's thrilling shootout, when they plundered the famed sandbelt course for 17 birdies, were extinguished early in the back nine when Poulter made a hash of the par-fives at 12 and 14.
The Englishman found a fairway trap and then a greenside bunker to bogey the 12th, then overcooked an approach shot two holes later to slip three strokes back with four to play.
The Ryder Cup hero clawed a stroke back with a birdie on the sixteenth to pull within two but was kicking himself after he missed a two-foot tap-in when reaching over Scott's line.
That bogey allowed Scott a care-free stroll up the last and the affable Australian finished in style, punching the air after curling in a 10-foot putt for birdie to the soundtrack of a roaring home gallery.
Scott came to Melbourne desperate for success after a consistent season tinged with frustration, and with queries over his mental fortitude in the wake of his spectacular collapse at the Open.
Scott had blown a four-stroke lead at Lytham with bogeys on his last four holes, but the Australian showed ice in his veins at Kingston Heath where he holed nine straight pars, including a 15-foot clutch-putt on the 11th to cling to his lead.
"I didn't want to let another opportunity to slip by," Scott said. "It was good to get back in that position and close a tournament out. That's what I need to do and I'm very happy with that."
Poulter had been in white-hot form after inspiring Europe to victory in the United States in September and winning his second World Golf Championship title in Shenzhen earlier this month.
But the Briton's aggression ultimately punished him as he came unstuck when attacking the pins on the back nine.
"I did make a couple of mistakes, so Adam, he played very solid and forced me into a couple of silly mistakes, but a worthy winner how he's played today," said the 36-year-old, the overnight leader by a stroke.
"It's a good week, it was good to try and defend. I'm obviously just a little disappointed that I wasn't slipping another jacket on."
Gareth Paddison shot a 68 to finish joint third with fellow New Zealander Mark Brown, eight strokes behind Scott.
Northern Irishman Graeme McDowell shot a 71 to finish joint eighth, a further seven strokes adrift.
"I'm not quite sure whether I had it on the greens here to really compete," the 2010 US Open champion McDowell said greenside.
1 Adam Scott -17
2 Ian Poulter -13
T3 Gareth Paddison -9
T3 Mark Brown -9
5 Adam Crawford -6
T6 Peter Senior -4
T6 Michael Hendry -4
T8 Graeme McDowell -2
T8 David Bransdon -2
T10 Matthew Millar -1
T10 Jake Higginbottom-1
T10 Matthew Guyatt -1
T10 Richard Green -1