Japan's Nakajima dominates Indian Open for first DP World Tour win
Nakajima finished with a 17-under par total of 271 with fellow Indian Veer Ahlawat, Sweden's Sebastian Soderberg and American Johannes Veerman sharing second on 13-under.
The former amateur world number one led after every round at the DLF Golf and Country Club near New Delhi and had a four-stroke cushion over Malaysia's Gavin Green starting the final day.
"It feels amazing," said Nakajima, who became the fifth Japanese player to win on the European-based circuit.
"I was a little nervous and I had a tough back nine but I hit some great shots.
"Fortunately I had a few strokes in the bank which I can credit back to my strong play on the front nine and the earlier rounds this week, so overall very proud of my performance."
"I want to try and finish in the top 10 on this tour and then go to the PGA Tour in 2025."
Nakajima began the final round in untroubled fashion, opening up a nine-stroke lead at the turn.
But he ran into trouble on the back nine, starting with a double-bogey on the 14th.
He clawed one stroke back on the next by sinking a 20-footer but then missed three successive greens to finish his one-over par round of 73 with bogeys on each of the final three holes.
Soderberg also dropped a shot at the last to finish with a 67 but Ahlawat gave the home crowd something to cheer when he sank an eagle putt on the 18th to get into a share of second place after a 71 laced with four bogeys.
Veerman closed with a bogey-free 67 but Green fell away with a two-over 74.
This season is the first in the DP World Tour to have multiple Japanese winners after Rikuya Hoshino won last February's Qatar Masters.