The 22-year-old from the Gold Coast, son of former tennis star Liz Smylie, produced a string of clutch par saves and dodged Smith's last desperate swings in a bogey-free Sunday at Royal Queensland.
His 14 under total (65, 67, 67) left him two clear of three-time winner Smith (67, 65, 69), who was level with Smylie to begin Sunday but again stuttered on the final day after blowing a final-round lead at the NSW Open last weekend.
Cool as you like from Elvis Smylie — PGA of Australia (@PGAofAustralia) #AusPGA pic.twitter.com/BXXwncVJlkNovember 24, 2024
"It's a dream come true ... I won't forget this day playing with Cam and Leish," he said.
"My short game was great; I definitely saved myself."
Smylie and Smith traded birdies to begin their rounds but it was the protege - Smylie won former world No.2 Smith's scholarship in 2019 - who produced down the stretch with five gutsy par saves despite missing fairways and greens to move four clear of Smith with four to play.
LIV Golf star Smith had to take relief when he found the mangroves on the ninth and then missed a par putt after finding trees again on the 14th.
He kept swinging though, a birdie on the 15th and brilliant chip-in from behind the 17th party hole green getting him within two shots with one hole to play.
Cameron Smith found trouble on the back nine as he lost touch with Elvis Smylie. (Jono Searle/AAP PHOTOS)
A wayward drive meant Smylie had to curl his second shot from behind a tree, but he kept his cool again to get up and down from the greenside bunker to ice the win.
Smylie had a one-shot lead after the first round before rain scrapped all play on Friday and the event was reduced to a 54-hole spectacle.
Smith was on song when he carded a six-under 65 on Saturday but Smylie rallied to ensure they shared the lead overnight.
Anthony Quayle came from the clouds with a final-round 63 to finish third at 11 under alongside Marc Leishman, who added another top-five finish thanks to a round of 69 full of near misses.
Marc Leishman has claimed another top-five finish thanks to a solid final round in Brisbane. (Jono Searle/AAP PHOTOS)
Smylie was a prodigious amateur who battled on his first season in Europe before COVID-19 hit, the left-hander overhauling his team and finding joy with a professional breakthrough victory at last month's WA Open.
Smylie will get another crack in Europe, his $323,000 cheque coming with a two-year exemption on the DP World Tour.
David Micheluzzi, who has just finished his maiden European tour and showered Smylie in water on the 18th green, finished fifth at 10 under.
Jason Day loomed before a double bogey on the 14th - only his third dropped shots for the tournament - saw him sign for a 69 to be eight under and equal eighth in his first Australian event in seven years.
Defending champion Min Woo Lee almost missed the cut and complained of a sore knee from a "freak" accident but rallied with a five-under 66 to finish a shot further back from Day.