'That has taken a lot out of me,' said Atwal, who led wire-to-wire. 'Leading from the first day is mentally tough and, while it didn't get to me on the golf course, I feel drained. This victory makes me believe in myself a bit more. This one tells me I am good enough to play on The European Tour.'
Retief Goosen, who got within one shot three times, and Brad Kennedy tied for second place at 20-under-par 264. Dean Robertson finished alone in fourth at 18-under-par 266, while Thammanoon Srirot was one stroke further back at minus-17.
The tournament was a two-man race, between Atwal and Goosen, heading into the final round. Atwal led by two strokes after the duo completed their third round Sunday morning.
Goosen closed to within one shot with a birdie at the first hole. Atwal responded with back-to-back birdies from the second to stretch his lead to two as Goosen also birdied the third. Goosen got within one shot again with a birdie at the par-4 fifth.
Atwal, who last year became the first Indian to win on the European Tour, created breathing room as he took a two-shot lead with a birdie at the sixth. Both players would par the final three holes on the front side.
On the back-nine, Goosen closed to within one stroke for the final time with a birdie at the par-4 10th. The South African faltered with a bogey at the 13th after his tee shot found water to drop two shots off the pace.
'I hit a terrible two iron on the 13th into the water,' said Goosen. 'And that was a bit of a turning point but once again I had a chance of making a four but left (my putt) short.'
Atwal quickly extended his lead to three shots with a birdie at the par-3 14th. He closed out his second European title in fine fashion as he chipped in for birdie on the 18th for the four-shot win.
'It was fun playing against Retief,' said Atwal, who won the Caltex Singapore Masters last year. 'I was on top of my game. I'm not sure he was on top of his game but he finished 20-under-par on this golf course.'
Goosen, the world No. 5, was gracious in defeat.
'I putted badly,' said Goosen. 'The greens really slowed up this afternoon with the growth and unfortunately I couldn't stroke the ball hard enough. But Arjun played very well and holed a lot of good putts. I can't take anything away from him, he played well.'
Kennedy began his round six shots off the pace and never threatened Atwal's lead. Entering the final round at minus-13, the Australian got moving quickly with a birdie at the first. However, he gave the stroke back with a bogey at the third.
Kennedy carded birdies on Nos. 6 and 9 to head to the back side at 15-under. Around the turn, he birdied the 11th before converting consecutive birdies beginning at the 13th. Kennedy climbed into a share of second place as he birdied the final two holes for a score of 64, the lowest total of the final round.
'I played really well today - I had it in the groove,' said Kennedy. 'I had a couple of great swings coming in and holed a good putt on the 17th so I'm delighted with the finish.'
Daniel Chopra finished alone in sixth place at 16-under-par 268 after a final round 69. Ted Oh was one stroke behind him at minus-15, while Patrik Sjoland shot a final round 66 to finish at 14-under-par 270.
Simon Dyson, Simon Khan, Wen-Chong Liang, Gerald Rosales and Wei-Tze Yeh tied for ninth place at 13-under-par 271.
Defending champion Alastair Forsyth closed with back-to-back rounds of 68 to finish at 7-under-par 277, which tied him for 33rd.
The tournament had been plagued by thunderstorms on Friday and Saturday causing the third round to be completed Sunday morning. Play was delayed again Sunday by more thunderstorms, but the weather broke and play was able to be finished.