KUALA LUMPUR, 8 Feb 2015 (AFP) - Lahiri had vaulted into contention the day before with a tournament-low ten-under 62, and followed up with a final-round 68 for the win.
"I don’t think it has sunk in just yet but I’m pretty sure when it does, I’ll be pretty happy," said the 27-year-old.
"I’ve got a bad habit of making it hard for myself, but I’m happy I managed to get it over the line."
The Malaysian Open is co-sanctioned by the European and Asian Tours, and the win was Lahiri's sixth on the Asian circuit.
Lahiri began the day five strokes behind third-round leader Wiesberger, who had shot to the top of the boards Saturday with a European Tour personal-best nine-under 63 at the tricky Kuala Lumpur Golf and Country Club.
But on the par-five fifth hole Sunday, Wiesberger chunked his third shot into a water hazard for a costly double bogey, opening the door for Lahiri.
The Indian charged through with his early birdie blitz. Despite a couple of later bogeys, he fended off the faltering Wiesberger, who suffered three bogeys on the back nine to card a two-over 74 for the day.
"It hasn’t quite finished the way I intended to," Wiesberger said.
"After the hiccup on five, I didn’t hit it anywhere near as good as the last 15 rounds. It’s tough to say, but it is what it is and unfortunately I beat myself out of it today."
England's Paul Waring and the second round co-leader Spain's Alejandro Canizares finished two strokes behind Wiesberger in a tie for third on a breezy yet scorching day.
England's Lee Westwood had held the co-lead after each of the first two days and remained in the hunt when the final round started.
But his chances of defending the title he won last year crumbled as he posted a disappointing 75 to end in a four-way tie for fifth, five strokes back of Lahiri.
Westwood, who has won the tournament twice and seems to play some of his best golf in Asia, is notably comfortable with the Malaysian Open course's undulating fairways.
But after a strong start, his birdie count dropped each day while several other golfers seemed to get hotter.
The European Tour said Lahiri's performance could move him to within the top 40 in the world golf rankings -- from 73rd before the tournament -- putting him in line to play the upcoming Masters, golf's most sought-after individual prize.
"The Masters is definitely one of my targets. I don’t know how far I moved up but I’m pretty confident now that with this win, I should have a good chance," he said.
Leading final-round scores on Sunday in the $3 million Malaysian Open at Kuala Lumpur Golf and Country Club (par 72):
272 - Anirban Lahiri (IND) 70-72-62-68
273 - Bernd Wiesberger (AUT) 70-66-63-74
275 - Paul Waring (ENG) 69-68-65-73, Alejandro Canizares (ESP) 68-65-68-74
277 - Gregory Bourdy (FRA) 70-70-68-69, Richard T. Lee (CAN) 69-69-68-71, Paul Peterson (USA) 72-69-64-72, Lee Westwood (ENG) 66-67-69-75
278 - Marc Warren (SCO) 70-71-69-68
279 - S.S.P Chowrasia (IND) 76-67-68-68
280 - Wade Ormsby (AUS) 73-69-71-67, Nathan Holman (AUS) 72-71-71-66, Richard Bland (ENG) 68-70-73-69
281 - Scott Hend (AUS) 73-72-66-70, Wang Jeung-hun (KOR) 77-66-67-71
282 - Robert Rock (ENG) 70-70-74-68, Peter Lawrie (IRL) 71-66-75-70, Thomas Pieters (BEL) 73-73-70-66, Peter Uihlein (USA) 72-72-65-73