CADIZ, April 6, 2014 (AFP) - The 35-year-old took victory on his 25th career start after a final round of three under par 69 gave him a ten under total.
It was enough for a two-shot win over Spain's Jordi Garcia Pinto and Scotland's Richie Ramsay.
The two-time Challenge Tour winner had only finished in the top ten of a European Tour event once before, finishing fourth at the South African Open earlier this season.
But he held his nerve and birdied the 14th before parring his way in for victory.
"I started very well today. I birdied the first and that gave me the confidence to go low," said Crespi.
"I just had to manage my pressure on the back nine. "I lost a couple of shots on 12 and 13. On 12 I hit a very bad eight iron to the green, my only bad shot of the day. On 13 I had a very long iron, a three iron, and it wasn't a really bad shot.
"But then I birdied the next; I really like the 14th because I birdied it every day. I played very good and I am very happy."
Leading fourth round scores in the Cadiz Open on Sunday (GBR/IRL unless stated, par 72):
278 - Marco Crespi (ITA) 70 73 66 69
280 - Richie Ramsay 71 72 69 68, Jordi garcia Pinto (ESP) 73 70 71 66
281 - Felipe Aguilar (CHI) 71 69 70 71, Matthew Nixon 72 71 65 73
282 - Marc Warren 72 67 75 68, Kristoffer Broberg (SWE) 76 70 67 69, Adrian Otaegui (ESP) 71 69 72 70, Oliver Fisher 71 72 71 68
283 - Ricardo Santos (POR) 74 70 67 72, Bradley Dredge 70 69 78 66
284 - Tjaart Van Der Walt (RSA) 70 73 69 72, David Horsey 71 68 73 72, Phillip Archer 74 70 73 67, Rhys Davies 72 71 72 69, Gary Stal (FRA) 72 74 73 65
285 - Damien McGrane 74 69 70 72, Daniel Im (USA) 72 72 71 70
286 - Matteo Delpodio (ITA) 71 73 70 72
287 - Andrew Johnston 73 72 70 72, Jamie McLeary 73 70 74 70, Connor Arendell (USA) 72 75 70 70, Lasse Jensen (DEN) 73 70 74 70, John Hahn (USA) 74 68 75 70, Carlos del Moral (ESP) 73 72 72 70, Edouard Dubois (FRA) 73 73 74 67, Alexander Levy (FRA) 72 75 72 68
288 - Byeong-Hun An (KOR) 73 73 76 66, Maarten Lafeber (NED) 78 69 73 68, Mark Foster 71 77 73 67