The Northern Irishman arrived in Dubai level with Ernie Els for most wins at this event but entered the weekend ten shots back after starting his week 71-70.
With a stacked field to overcome in the first Rolex Series event of the season, McIlroy knew he needed to do something special to defend his title and he produced just that with a brilliant bogey-free 63.
A remarkable eagle putt from off the green on the par-five last moved him to 12 under and the World Number Two was excited to have the chance to win a third Rolex Series title, sixth event in Dubai and fourth Dallah Trophy.
"It would be amazing," he said. "First player to get my name on it four times, it would be awesome.
"I've had so much success in Dubai, whether it be at this tournament or over at Jumeirah Golf Estates and Race to Dubais. It's been a really, really good place to me.
"I love coming back here. I really enjoy my time here. It would be amazing if I was able to get another win."
McIlroy got going with a brilliant shot from the rough to two feet at the first and while he missed out at the gettable second, he got up and down for birdie at the par-five third.
A golden patch then followed with his irons as he put a tee-shot to seven feet at the seventh, an approach to similar range at the eighth and a towering eight iron to five feet at the ninth to turn in 30.
The 34-year-old had birdied the par-five tenth and 13th on days one and two and he took advantage again with an up-and-down and a two-putt but better was to come.
He had a lot of fringe to get through on the 18th but took out the putter and rolled home a 45-foot left-to-righter to send the bumper crowds wild.
"I was walking up with the putter in my hand and as I got closer to the ball I saw that there was a lot of fringe to go through," he said of the 18th.
"And I said to (caddie) Harry (Diamond), I sort of want to chip it but the lie wasn't great. I could just see the club bouncing.
"I was like, I'll just sort of ride my luck with the putter and it came out perfectly. As soon as it got on the green, it actually wasn't as fast as I thought it was going to be once it got on the green, and it was tracking perfectly. Obviously a huge bonus for something like that to go in.
"But you know, for the rest of the day, I played some very, very good golf. Definitely better than I played the last couple of days and nice to get myself right back in the tournament.
"I've played the front nine a little scrappily the last couple of days.
"I was a couple under through three and I thought if I could pick one or two more up from that tough stretch from five through nine, and I ended up picking three up - birdieing seven, eight and nine, which was fantastic.
"And then I just kept it going into the back nine.
"I think for me, the key to this golf course is always the front nine because it is the tougher nine and if you can play that nine well, you give yourself a ton of momentum going into the more scorable back nine."