Bidding for rare back-to-back triumphs, McIlroy laid down a marker with an opening five-under-par 67 to be the first defending champion since Jordan Spieth a decade ago to capture at least a share of the first-round lead.
"I felt like I got a lot out of my round. It started pretty scrappy," said the world No.2 who sits atop the leaderboard with American Sam Burns.
"I was hitting out of the trees a little bit the first seven holes and then started to string some good swings together from the eighth hole onwards and played those last 11 in five under.
"I stayed really patient when I needed to."
Striving to become only the fourth man after legends Jack Nicklaus, Tiger Woods and Nick Faldo to retain the green jacket, McIlroy burst to life with five birdies in eight holes.
The Northern Irish superstar and Burns are two shots clear of 2018 champion Patrick Reed, fellow American Kurt Kitayama and Australian Jason Day.
Plenty of other stars are lurking on a leaderboard of just 16 players in red figures after baking-hot greens left the bulk of the 91-strong field languishing over par.
England's sentimental favourite Justin Rose, who lost a dramatic play-off last year to McIlroy and also one to Sergio Garcia in 2017, world No.1 and two-time champion Scottie Scheffler and fellow major winners Shane Lowry and Xander Schauffele are bunched on two under.
But McIlroy warned the chasers he was playing with the bank's money after finally ending an 11-year wait to complete the elusive career grand slam with his momentous 2025 victory.
"I think winning a Masters makes it easier to win your second one. I do," he said.
"It's hard to say because there's still shots out there that you feel a little bit tight with and you just have to stand up and commit to making a good swing and not worry about really where it goes.
"But I think it's easier for me to make those swings and not worry about where it goes when I know at the end of the day that I can go to the Champions Locker Room and put my green jacket on and have a Coke Zero."
McIlroy, though, did confess to feeling anxious teeing off at the first.
"We're playing the first major of the year. It's the Masters," he said.
"If I felt absolutely nothing on that first tee, that's not a good sign.
"So it was nice to feel my hand shaking a little bit. I knew I was feeling it. That's a good thing."
The well-fancied Bryson DeChambeau, coming off successive LIV Golf wins and paired with McIlroy for last year's final round, needed three attempts to escape a greenside bunker at 11 en route to a triple-bogey seven and a four-over 76.
"Bunker was softer than I anticipated," DeChambeau said.
"The ball flew 12 yards further than I wanted it to. I had a good shot."
At 66, the great Freddie Couples was making an inspired charge, reaching the 15th at two under before also coming unstuck.
The 1992 winner despairingly drowned two balls in Rae's Creek to pile up a quadruple nine and eventually signed for an imploding six-over 78.
14°C