The Englishman, who triumphed at St Andrews last Sunday, claimed back-to-back victories with a final-round 65 in Monza when he holed a 15-foot birdie putt on the 18th green to edge past clubhouse leaders Ross Fisher and Kiradech Aphibarnrat to 21 under par.
He birdied five of the last seven holes as he timed his run to perfection, and later revealed caddie Jonathan Bell’s advice had proved key.
Hatton said: “It’s amazing to win one, but to win back-to-back and defend in two weeks is unbelievable.
“I knew I needed a low score today, and the front nine was pretty slow and I didn’t really get any momentum.
“I was fighting myself, trying to stay patient and JB, my caddie, was saying, ‘Good things will come’.
“Although I found it hard to believe, I tried to stay patient. In the end, I guess I got my reward.
“The end goal is to get as high as possible up the world rankings.
“Obviously the last two weeks have helped a lot.”
Hatton was pushed all the way by compatriot Fisher, who shot an eight-under-par 63, and Thailand’s Aphibarnrat as they finished joint-second on 20 under par.
Fisher, who set a new course record at St Andrews with a round of 61 last Sunday, birdied three of the first four holes to set up his charge but finished with four fours.
Aphibarnrat launched his assault with birdies at each of the first four holes, but a double bogey at the 16th cost him dearly.
It proved to be a disappointing day for overnight leader Matt Wallace, who carried a two-shot lead into the final round.
Just two birdies on the outward nine left the Englishman under pressure and a bogey six at the 14th proved costly, despite chipping in from behind the green on 17 to keep his hopes alive.
His chance was gone when he found a green-side bunker at the last and emerged with only a par to remain on 19 under and finish in fourth place.