Chacarra, who won the Dutch Open and the 83 Open d'Italia in June and the Indian Open last year, finished on 21-under at Delhi Golf Club.
Chacarra will move to the top of the Race to Dubai rankings, overtaking Patrick Reed, who finished eight-under.
The 26-year-old Chacarra carded a final-round two-under-par 70 and pumped his fist in the air to celebrate his third win on the European Tour this season.
New Zealand's Daniel Hillier was second on 19-under, and Chacarra's fellow Spaniard Angel Hidalgo and Poland's Adrian Meronk were tied third on 15-under.
England's Tommy Fleetwood, the defending champion, finished tied fifth at 13-under.
With the tournament playing catch-up, Chacarra completed his third round in the morning to extend his sole lead.
He kept up the charge in the final round with three birdies against one bogey.
Six-time major champion Rory McIlroy, who had been in the hunt after the weather-disrupted first two days, finished tied 42nd at four-under.
"Last week it was really tough (broken toe), but this week doing all the ice and taking all the medications was better," said Chacarra.
"But my neck was just a bad position at night on Monday. My physio did a great job and made me compete.
"And playing at less than 100% and to be able to win against this field gives me great motivation."