Overnight leader by four strokes, US Masters champion Scott had appeared poised to canter to victory on a breezy day at Royal Melbourne, but was forced to grind out the win as Kuchar roared into contention with a scintillating front nine.
After forging two strokes clear by the time he reached the 16th tee, Kuchar fell back into a share of the lead with a bogey on the tough par-four and then handed the initiative to Scott with a double-bogey six after finding sand on the last.
Playing a couple of groups behind the American, Scott was in no mood to give up the two-shot lead he suddenly inherited and was able to soak up the adulation of a massive home gallery when he tapped in a three-foot par putt on the last to seal victory.
"I guess today, sometimes you kind of win a little bit ugly," Scott told reporters after carding a scratchy even-par 71 for a 14-under total of 270 and a winner's cheque worth A$186,000.
"All of the good stuff I'd done in the first three rounds counted for a lot.
"Even though it wasn't the prettiest golf today... I got away with it, but I'll have to learn not to do it next time."
Former No 1 Vijay Singh, joint second overnight, was quickly out of the picture after toiling early, leaving the title to be decided by a shoot-out between Scott and Kuchar.
Having played the famed sandbelt course with aplomb on the opening three days, Scott had trouble selecting the right clubs and ground his way to the turn on even-par as Kuchar soared to four-under for the day.
The 33-year-old Scott stumbled badly on the par-three 14th, his sand wedge off the tee coming up short and burying itself in a green-side bunker.
Faced with a "fried egg" lie, Scott's recovery raced off the green, leading to a double-bogey that handed Kuchar a two-stroke advantage.
"That one was completely on me because (caddy) Steve (Williams) wanted me to hit wedge but I just didn't have the feel for a wedge," Scott said.
Unbowed, Scott bounced back with a birdie on the next hole to put the heat back on Kuchar and was a model of composure as he completed the course with three straight pars.
Wearing the winner's 'gold jacket', Australia's answer to the more prestigious green one given at Augusta, Scott beamed as he pondered his second title in a week following his Australian PGA Championship win at the Gold Coast last week.
Scott has a chance to sweep all three of Australia's marquee tournaments when he lines up at the national Open in Sydney later this month, but will return to Royal Melbourne in a few days to team up with compatriot Jason Day for the World Cup starting on Thursday.
"Come back next week and see me and Jase," Scott urged fans at the trophy presentation. "We'll win the World Cup."
Image: Adam Scott of Australia kisses the trophy
Photograph: Scott Barbour/Getty Images
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