McIlroy bounced back from a turbulent week to clinch victory at the European Tour's flagship BMW PGA Championship on Sunday at the Wentworth Club in Surrey.
The double major winner was seven shots back at the start of the final round but rallied to shoot a 6-under 66 and win by one stroke with a 14-under 274 total on the Surrey layout.
McIlroy’s last win on any tour was the 2013 Emirates Australian Open in December.
Shane Lowry of Ireland was second with a round of 68 for a 13-under 275. Denmark'sThomas Bjorn (75) shared third place on 12 under with England's two-time BMW PGA winnerLuke Donald (70).
McIlroy's 12th victory worldwide comes just four days after the 25-year old Northern Irishman confirmed the end of his engagement/relationship with Danish tennis star Caroline Wozniacki.
"I guess when I got inside the ropes this week, it was a little bit of a release, and I was on my own and doing what I do best, which is playing golf, and that sort of gave me four or five hours of serenity or sanctuary or whatever you want to call it," McIlroy said.
"I was just focusing on the job at hand which was to play golf and get the ball in the hole in the lowest number of shots possible … It's obviously been a week of very mixed emotions, but I'm sitting here looking at this trophy going, `How the hell, how did it happen this week?' But it did."
It was McIlroy's first success since coming from behind to win the Australian Open in Sydney. He heads into next month's U.S. Open as a strong contender to win the event for a second time in four years.
"The win at the end of last year in Australia sort of stopped all the questions about equipment and about struggling and slump and all this stuff," McIlroy said.
"But to win here, against a great field, one of the best fields of the year, especially in Europe sort of cements that, and shows where my game is and I'm on the right track again. Hopefully, it won't be long before I'm contending in majors and having a chance to win those again."