FINAL ROUND LEADERBOARD:
-21 P Casey (GB) -20 L Oosthuizen (Rsa) -18 M Kaymer (Ger)
Selected others: -17 P Harrington (Irl), R McIlroy (NI) -16 S Garcia (Spr), -14 G Storm (GB), -8 C Montgomerie (GB)
This is Casey's first title since winning the same tournament in 2007
Paul Casey ended his two-year winning drought by securing the Abu Dhabi Championship, but only by a stroke.
Six shots clear with six holes to play, Casey saw his lead cut to one when he shot three bogeys and Louis Oosthuizen posted a final-round 64.
However, Casey parred the last four holes for a round of 70 and claimed the title with a 21-under-par total of 267.
Defending champion Martin Kaymer tied for second, while Padraig Harrington and Rory McIlroy shared fifth.
Having begun the day four shots clear of his nearest rival the newly married Casey quickly increased his lead to six with birdies at the opening two holes and then the sixth to move to 22 under.
Kaymer maintained slender hopes of a challenge by remaining in second but was joined by both Harrington, who birdied five of the first eight holes, and Swede Johan Edfors.
Casey two-putted the long eighth for another birdie, that Kaymer matched, before the latter birdied the next hole to cut the lead to five.
As Harrington fell away, partly due to a bogey at the ninth, South African Oosthuizen swept into contention courtesy of five birdies in eight holes either side of the turn to leave him three behind.
Casey, having registered his fifth birdie at the par-five 10th, then bogeyed the 11th, 13th and 14th before composing himself to secure victory.
"That was a bit of a nervous one," admitted the former World Match Play champion, whose last victory came in the same tournament in 2007.
"I didn't think I would have to wait so long. My game is now better than it's ever been and I've played some great stuff in spurts, but I've never really put it together.
"I've been focused on the majors, and performed well, and maybe neglected other tournaments. That's what I'm trying to do and it looks like it's paying off."
"It feels like a pay-off for all of the worrying I've put in over the past couple of months. It shows that marriage is clearly good for me."
Casey, 31, married American Jocelyn Hefner in December.