PERTH, 26 Oct, 2014 (AFP) - Dubuisson went into the final round eight shots adrift of overnight leader Olesen, but the Frenchman whittled down the gap to two strokes in a sizzling six-under-par round of 66 at Lake Karrinyup.
Olesen looked shaky after posting bogeys on the sixth, 10th and 12th holes, but the 24-year-old Dane birdied two of his next three holes to secure his second European Tour win after closing with a 71.
Olesen's last win came at the 2012 Sicilian Open and he finished sixth at last year's Augusta Masters.
The world No.130 Olesen, who finished at 17-under 271, is now guaranteed a spot in the Race to Dubai finals series.
"Before this week I was struggling. I was 64 in the ranking and I was not even sure if I was getting into next week," Olesen said.
"It's a big relief and a big confidence boost to get into the last four events."
Dubuisson finished three strokes behind Olesen at 14 under, while England's Mark Foster (69) finished third at 12 under.
"It was very emotional out there," Olesen said.
"It was up and down and I didn't play my best golf, but I kept fighting and made some great putts there in the end.
"I didn't play my best golf these two days, and to keep fighting out there and keep believing in myself, I'm very proud of what I did there."
Dubuisson later revealed he had been battling a fever.
"I was feeling so bad this morning. My muscles were hurting," he said.
"But then when I started to play I tried to not think about it. Just on the last few holes it (affected) a little bit my game, but I made some good par putts to save."
South African Charl Schwartzel, the 2011 Augusta Masters champion, finished eight strokes behind Olesen in a tie for 15th on nine under after carding a final-round 72.
Leading scores after the final round of the Perth International at Lake Karrinyup (par-72) in Perth on Sunday (Australian unless stated):
271 - Thorbjorn Olesen (DEN) 64-69-67-71
274 - Victor Dubuisson (FRA) 71-67-70-66
276 - Mark Foster (ENG) 67-73-67-69
277 - Matthew Griffin 67-73-70-67, Stephen Dartnall 68-71-68-70, Lucas Bjerregaard (DEN) 71-70-66-70, David Drysdale (SCO) 67-68-71-71, James Morrison (ENG) 72-63-69-73
278 - Wade Ormsby 72-68-72-66, Ryan Fox (NZL) 69-70-72-67, Andrea Pavan (ITA) 71-70-67-70, Richard Green 68-68-70-72, Peter Uihlein (USA) 69-71-65-73, Sihwan Kim (KOR) 66-68-69-75
279 - Jason Scrivener 67-74-70-68, Marcus Fraser 68-70-71-70, Mikko Korhonen (FIN) 71-70-67-71, Charl Schwartzel (RSA) 68-69-70-72
Selected scores:
281 - Richard Bland (ENG) 68-72-70-71, JB Hansen (DEN) 71-68-69-73
282 - Matthew Nixon (ENG) 70-71-69-72, Jason Dufner (USA) 70-70-69-73, Gary Stal (FRA) 69-71-67-75
283 - Gregory Bourdy (FRA) 69-72-71-71
284 - Carlos Del Moral (ESP) 71-72-69-72, Jamie McLeary (SCO) 70-71-69-74
285 - Magnus A Carlsson (SWE) 67-76-69-73, Kevin Phelan (IRL) 72-69-72-72, Peter Whiteford (SCO) 66-66-75-78
286 - Stuart Manley (WAL) 73-68-72-73, Damien McGrane (IRL) 70-70-73-73, James Heath (ENG) 72-71-70-73, Ricardo Gonzalez (ARG) 68-74-72-72, Soren Hansen (DEN) 72-71-71-72
287 - Julien Quesne (FRA) 67-73-72-75, Jack Doherty (SCO) 69-72-72-74, Soren Kjeldsen (DEN) 69-71-74-73, Simon Wakefield (ENG) 72-67-75-73
288 - John Parry (ENG) 69-72-73-74, Nacho Elvira (ESP) 71-71-74-72, Craig Lee (SCO) 73-69-75-71, Roope Kakko (FIN) 72-71-74-71
290 - Daan Huizing (NED) 68-73-73-76, Tom Lewis (ENG) 66-74-76-74
295 - Scott Jamieson (SCO) 69-74-71-81