The four-time major winner shot a final round 70 to claim his 10th European Tour success.
Sweden’s Alex Noren shot a final round 65 to finish second on 19-under-par and three clear of double defending champion Stephen Gallacher of Scotland, who posted a 69 for a 16-under-par total.
McIlroy’s victory ended a run of three straight second place finishes, stretching back to last year.
“It’s been a fantastic week for everyone who played here this week and it’s just nice to get my name on that trophy again,” said McIlroy.
“So I am very delighted because I was feeling like I was playing for second every time I was teeing it up, so it was time for a change and the only way I wanted to go was one better and thankfully I was able to do that today."
McIlroy went into the last round of his second event of the year leading by four shots at 20-under-par, but it was a slow start for the 25-year-old, who was level par after nine holes with a third hole birdie and a bogey at seven.
McIlroy then went five clear of his rivals with a birdie at 10 and another on 13.
He then ended with five straight pars and missed a 20-foot birdie putt at the last that would have seen him card a 23-under-par tournament record.
Despite the apparent ease of his victory, McIlroy said he still gets nervous and was also conscious of recent European Tour collapses from Charl Schwartzel at the South African Open and US Open winner Martin Kaymer in Abu Dhabi.
“I do still get nervous and felt I was a little tentative the first few holes out there because I guess we have seen what can happen to big leads over the past few weeks with Martin and Charl, so I was conscious of that,” he said.
"So I was trying hard not to make any mistakes and happy I was able to play a solid round.
"But the thing I do is that I set myself a target that tries to take everyone else out of it... While I didn’t quite get to the number I set myself I was still able to do enough."
(Reporting by Bernie McGuire; Editing by Toby Davis)
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