The world number 11 shot a last round 69 in the European Tour tournament, to go with previous rounds of 70, 67 and 68, to finish on 14 under.
In doing so he became the first player ever to win back-to-back Qatar Masters' titles, despite describing his chances of winning again in Doha as “slim” at the beginning of the week.
He finished two shots ahead of Spain's Rafa Cabrera-Bello, who shot a final round 70, and Denmark's Thorbjorn Olesen, who birdied the last for a 71.
One shot further back were a group of players on 11 under including Bradley Dredge and Andrew Johnston.
Overnight leader Paul Lawrie had a shocking last round, shooting a six over par 78, to finish at seven under. – AFP
Original source: Grace retains Qatar Masters title