The Englishman finished four clear of Brandon Stone to win the Dubai Desert Classic
Emotional Casey Wins 15th European Tour Title In Dubai
Watch: Casey's chip-in birdie at the par-3 4th -
MacIntyre started bright but four consecutive bogeys from the 7th-10th ended his hopes of a second European Tour win.
Casey now has 15 European Tour titles to his name, joining Padraig Harrington and Thomas Bjorn.
Related: Paul Casey What's in the bag?
The victory gives his Ryder Cup and Olympic bids a huge boost, with Casey very keen to make both sides this year.
He is set to move back inside the world's top 15.
"Very very special, it's an unbelievable roster," an emotional Casey said after adding his name to the likes of Tiger Woods, Seve Ballesteros, Colin Montgomerie and Rory McIlroy on the famous Dubai Desert Classic trophy.
"That's so cool, I've worked so hard. I feel like I've regained my youth, I'm so happy."
Watch: Casey birdies the 18th for 15th European Tour win
"I felt like I gave one away there today," a disappointed Robert MacIntyre said afterwards.
"I've just got to keep believing in myself. If I can keep giving myself chances I'm gonna bundle over the line at some point."
