TURIN, September 22, 2013 (AFP) - The 33-year-old went through the back nine in 31, picking up birdies at the 10th, 11th and 15th holes.
He then chipped in from short of the 17th green and putted from six feet for another birdie on the last to complete a closing 67.
That gave him a 12-under-par total and a one-shot win over Ireland's David Higgins and England's Steve Webster.
"I am very proud of this back nine. My attitude was very good this week and I think this is the key," said Quesne, whose previous title came at the Andalucia Open in 2012.
"To enjoy a second win on the European Tour is like a dream for me.
"I am surprised to be here. The flags were very difficult all week so it was very difficult to make birdies and easy to make some bogeys."
Overnight leader Marcus Fraser of Australia three-putted the 15th and dropped another shot on the par-three 16th.
Fraser eventually signed for a 74 to finish joint eighth on nine under.
Home hope Francesco Molinari, who joined the Turin club when he was just eight, came home in 39 to finish seven under.
Leading final round scores in the Italian Open at the Golf Club Torino on Sunday (GBR/IRL unless stated, par 72):
276 - Julien Quesne (FRA) 70 68 71 67
277 - Steve Webster 67 69 73 68, David Higgins 67 69 73 68
278 - Felipe Aguilar (CHI) 69 66 72 71, Emiliano Grillo (ARG) 70 72 68 68, Nicolas Colsaerts (BEL) 65 71 70 72, Fredrik Andersson Hed (SWE) 73 67 71 67
279 - Robert Jan Derksen (NED) 71 69 71 68, Hennie Otto (RSA) 71 67 70 71, Romain Wattel (FRA) 71 72 66 70, Marcus Fraser (AUS) 66 71 68 74, Seve Benson 68 70 72 69, Alvaro Quiros (ESP) 71 67 73 68
280 - Maximilian Kieffer (GER) 65 72 72 71, Espen Kofstad (NOR) 70 69 73 68
281 - Francesco Molinari (ITA) 68 67 71 75, Fabrizio Zanotti (PAR) 71 70 69 71, David Horsey 72 70 73 66, Jaco Van Zyl (RSA) 70 69 71 71, Simon Thornton 68 67 72 74, Mark Foster 74 65 71 71, Morten Orum Madsen (DEN) 72 71 70 68
282 - Mark Tullo (CHI) 70 70 74 68, Joakim Lagergren (SWE) 72 67 67 76, Jorge
Campillo (ESP) 68 73 70 71, Matthew Baldwin 71 68 72 71, Scott Jamieson 72 69 70 71, David Drysdale 69 72 71 70, Scott Hend (AUS) 72 71 66 73, Bernd Wiesberger (AUT) 69 72 68 73, Christopher Doak 74 67 69 72
Selected:
283 - Robert Allenby (AUS) 71 72 70 70
284 - Thomas Aiken (RSA) 69 71 74 70
286 - James Kingston (RSA) 68 71 75 72
287 - Garth Mulroy (RSA) 71 72 72 72
289 - Retief Goosen (RSA) 70 72 74 73, Justin Walters (RSA) 70 73 71 75
290 - Jose-Maria Olazabal (ESP) 71 68 74 77