LONDON, August 25, 2013 (AFP) - Fleetwood triumphed on the first extra hole at the Centenary Course, site of next year's Ryder Cup, to take the honours ahead of Scotland's Stephen Gallacher and Ricardo Gonzalez of Argentina.
Gallacher looked to have ruined his chances with a triple-bogey seven on the 11th hole, but he produced birdies at 14 and 16 before sinking a 15-foot putt to record an eagle on the last.
The Scot set a clubhouse target of 18 under par, but Fleetwood equalled his score thanks to a birdie on the last and playing partner Gonzalez matched his feat with birdies on 16 and 18.
The players returned to the par-five 18th for the play-off, and after Gallacher missed a seven-foot putt for birdie and Gonzalez three-putted, Fleetwood holed a birdie putt from four feet to claim the prize.
"The other two guys were a little unlucky with their putts and before you know it, you have a four-footer for the win," said Fleetwood.
"God knows how I made contact. It all seemed to unravel really quickly."
Fleetwood, 22, only kept his card at the end of his debut season on the European Tour by registering a first top-10 finish in the year's final event in South Africa.
He stayed with his parents in a house behind the 12th green at Gleneagles and added: "It's unbelievable. I have been up there a lot and not even had a top-five finish and all of a sudden you come away with a win.
"It just seemed to come a bit easier this week. I was nervous as hell on the first green but after that I was pretty calm.
"It was so tight, almost claustrophobic on the leaderboard; if you dropped a shot, you went down 10 places."
Gallacher's participation was cast into doubt after he hurt his back while washing his car on Monday, and he said he was pleased just to have been in contention.
"I would have taken a play-off on Monday," Gallacher said.
"I was just happy to be playing, to be honest. I actually hit the ball really, really well. It was only the short irons I was struggling with. I could not really get into my posture."
Collated leading final round scores in the Johnnie Walker Championship at Gleneagles on Sunday (GBR and IRL unless stated, par 72):
270 - Tommy Fleetwood 68 65 67 70 (Tommy Fleetwood won at 1st play-off hole), Ricardo Gonzalez (ARG) 65 65 70 70, Stephen Gallacher 71 68 64 67
271 - Scott Henry 72 65 67 67, Bernd Wiesberger (AUT) 65 66 72 68
272 - Brett Rumford (AUS) 66 69 69 68, Emiliano Grillo (ARG) 71 66 69 66, Paul Waring 75 63 67 67
273 - Thorbjorn Olesen (DEN) 71 68 66 68
274 - David Drysdale 71 67 68 68, Richie Ramsay 69 68 69 68, Shane Lowry 68 70 67 69, Mikko Korhonen (FIN) 71 69 67 67
275 - Craig Lee 69 67 71 68, David Horsey 70 68 69 68, Morten Orum Madsen (DEN) 70 70 67 68
276 - Gary Boyd 71 69 68 68, Ross Fisher 66 72 66 72, Anders Hansen (DEN) 70 69 68 69, David Howell 71 70 67 68, Tom Lewis 67 71 67 71, Thongchai Jaidee (THA) 66 69 73 68
277 - John Parry 71 66 70 70, Richard Finch 73 67 68 69, Espen Kofstad (NOR) 71 70 68 68, Gregory Bourdy (FRA) 68 71 70 68, Fredrik Andersson Hed (SWE) 68 67 66 76