McIlroy kept the ball in play at Quail Hollow and gave himself plenty of birdie chances on a cloudy, soft afternoon. He ran off six birdies in a seven-hole stretch around the turn and finished with an 8-foot birdie putt for a 5-under-par 67 to share the lead with six other players.
It was the first time this year McIlroy has been atop the leaderboard after any round, and the first time he broke par in the opening round.
Nick Watney, Ryan Moore, Robert Garrigus and PGA Tour rookie Derek Ernst shot 67 in the morning. Daniel Summerhays and Nate Smith, a Monday qualifier, joined McIlroy by posting their 67s in the afternoon.
The group one shot behind included four-time major winner Phil Mickelson and 2009 U.S. Open champion Lucas Glover.
LPGA TOUR: In Williamsburg, Va., teenager Ariya Jutanugarn shot 7-under-par 64 to take a two-stroke lead after the first round of the Kingsmill Championship.
The 17-year-old Jutanugarn was 8-under through 16 holes, but pulled her drive and had a double bogey on the par-3 17th before rebounding with her ninth birdie of the day on the par-4 finishing hole.
Cristie Kerr, the only-two time winner in the tour’s eight previous visits to the River Course, had six birdies and one bogey in 66 that put her alone in second place.
So Yeon Ryu and Dewi Claire Schreefel shot 67, and a huge logjam at 68 included top-ranked Inbee Park, No. 2 Stacy Lewis and former Kingsmill winner Suzann Pettersen.
WEB.COM TOUR: In Athens, Ga., former Georgia golfer Brendon Todd is tied for the lead after the first round of the Stadion Classic at UGA.
Todd shot 5-under-par 66 as did Rafael Echenique and Whee Kim. Brenden Pappas, Michael Putnam and Tim Wilkinson had 67. Augusta’s Scott Parel opened with 73.
EUROPEAN TOUR: In Tianjin, Robert-Jan Derksen shot 6-under-par 66 to take the first-round lead in the China Open, while 12-year-old Ye Wocheng opened with 79 at Binhai Lake.
At 12 years, 242 days, Wocheng became the youngest player in European Tour history. He broke Tianlang Guan’s mark of 13 years, 177 days set last year in the event.
Defending champion Branden Grace had 74.
ASIAN TOUR: In Jakarta, Indonesia, Scott Hend and Hwang Inn-choon shot 6-under-par 66 to share the first-round lead in the Indonesian Masters.
Bernd Wiesberger was a stroke back, and Ernie Els opened with 68 at Royale Jakarta.