After returning to the 18th tee for the play-off, Rumford, drawn against compatriot Marcus Fraser and Scotland's Peter Whiteford, fired a spectacular second shot which landed within six feet from the pin. The 35-year-old made no mistake in draining his eagle putt which made him the second Australian after Fraser to win the €2,205,000 (approximately US$2.8 million) Ballantine's Championship.
France's Romain Wattel closed with a three-under-par 69 to take fourth place while world number seven Louis Oosthuizen of South Africa was a further shot back in fifth place after signing for a 69 at the Blackstone Golf Club.
Three-time Asian Tour Order of Merit winner, Thongchai Jaidee of Thailand enjoyed his second top-10 finish on the Asian Tour after he equaled the course record of 65 to take a share of sixth place with Korea's Kim Hyung-sung, Scotland's Stephen Gallacher, Spain's Pablo Larrazabal and overnight leader Alexander Noren of Sweden on matching seven-under-par 281 total.
Rumford could have sealed his victory at the Ballantine's Championship in regulation play as he looked set to be cruising towards victory after an outward-30 at the Blackstone Golf Club.
He led by two shots with two holes to play until a double-bogey six on the 17th hole saw him lose the outright lead.
The 35-year-old, however ensured he was back in command during the play-off with his brilliant approach shot where he eagled to finally end his six-year title drought.
"It was a roller coaster day for me. One shot can really turn events, and obviously 17 proved that. I seemingly had everything under control, and I was thinking, it's just two good drives coming home and then I hit two into the trees which wasn't my ideal finish," said Rumford.
"It's an honour to win anytime, and it's only getting harder and harder. As the years go on, I'm getting older and there're more and more young guys coming through with really big games, and the face of golf is changing with technology and obviously with the fitness of these young guys coming through, the ball going so much further. So it's great to be in this position today and an honour to win the Ballantine's Championship," added Rumford.
Fraser, who was bidding to win his second Ballantine's Championship following his victory in 2010, tipped his hat to Rumford for being a deserving winner.
"I played very well this week and came up a little bit short. I got beaten by some pretty good golf today. That shot into the playoff hole was pretty impressive. He (Rumford) would easily agree it's one of the best shots he's ever hit to, so full credit to him.," said Fraser.
"I played the play-off hole really well. Hit the second shot a little bit left and hit a great chip to about a foot. But that wasn't good enough and that's the way it is, that's golf and we are big boys, we'll get over it I'm sure," added Fraser.
It was a heartbreaking moment for Whiteford as he could have sealed his win at the Ballantine's Championship with his birdie putt from five-feet on the final 18th hole.
The ball, however went inches off from the pin, leaving Whiteford deflated and searching for answers.
"I thought it was a decent putt but I obviously misread it. I'll take the positives, press on and see if I can go one better," said Whiteford.
After rounds of 71,72 and 73, Thongchai saved his best for last when traded eight birdies against one bogey for a 65.
"I'm enjoying my golf game right now. I've been hitting well all day and only three-putted once," said Thongchai.
"I'm quite pleased with that as the pin positions were tough and the course conditions made it hard to putt. However, it was warmer today and that made things a lot easier," added the 13-time Asian Tour winner.
The sixth edition of the Ballantine's Championship was the first event to be played in Korea on the Asian Tour this season and is once again sanctioned by the Asian Tour, European Tour and Korea PGA.