NEW DELHI, 22 Feb 2015 (AFP) - The 27-year-old, who was seven shots off the pace at the start of the day, fired a two-under-par 69 as overnight leader Chawrasia struggled in blustery conditions to record a disappointing 76.
Both players finished on seven-under-par 277 in regulation play. They returned to the 18th hole where Lahiri sealed victory with a birdie from inside 10-feet. Chawrasia's title hopes faded when his tee shot landed under thick branches.
The victory was Lahiri's seventh Asian Tour title and second European Tour win. He won the Malaysian Open two weeks ago.
Lahiri said he was delighted to fulfil his childhood dream by winning his national open.
"I really didn't think that I will be in this position considering the way S.S.P. and Siddikur have been playing. I thought all of us were playing for third," Lahiri said in comments supplied by the organisers.
"This has been a childhood dream so it is very special to keep the Indian Open trophy at home. Every Indian puts winning the Indian Open on their bucket list."
Lahiri took advantage of Chawrasia's stuttering form when he turned in 34 before trading one birdie against one bogey on the back nine. But it was a chip-in par on the 17th hole which kept him in the title race.
Chawrasia finished second for the fourth time in his national Open.
"It's been a great week and I played well for three days and had some bad shots in the final round, but it's OK. The problem today was the wind. It was gusting a lot and made it very difficult," he said.
Sri Lanka's Mithun Perera enjoyed his best result of 2015 when he posted a 69 to share third place alongside Thailand's Prayad Marksaeng (71), Marcus Fraser (72) of Australia and Joakim Lagergren (69) of Sweden.
Leading scores after round four of the Indian Open at the par 71, 6,923-yard Delhi Golf Club course:
277 - Anirban Lahiri (IND) 73-65-70-69, S.S.P. Chawrasia (IND) 65-67-69-76
278 - Joakim Lagergren (SWE) 65-71-73-69, Mithun Perera (SRI) 67-72-70-69, Prayad Marksaeng (THA) 68-70-69-71, Marcus Fraser (AUS) 69-70-67-72
279 - Romain Wattel (FRA) 70-74-67-68, Richard McEvoy (ENG) 70-67-72-70, Siddikur Rahman (BAN) 65-68-70-76
280 - Paul Peterson (USA) 69-68-71-72