With the top players in the men's game competing in this week's British Open, Lincicome entered the Barbasol on a sponsor's exemption.
Only one woman has made the 36-hole cut in a men's event -- Babe Zaharias in 1945.
"I was a lot calmer then I thought I was going to be, which was a relief," said Lincicome. "After that first tee shot I was like. 'OK let's go, we can do this.' It was just so much fun being inside the ropes with the guys."
Lincicome, who has two majors among her eight wins on the LPGA Tour, mixed a birdie with two bogeys, a double-bogey and a triple-bogey and will likely need a round in the mid-60s on Friday to have any hope of making the cut.
A long hitter on the women's tour, Lincicome started on the back nine and hammered her opening drive down the heart of the 10th fairway to set up a routine par.
Her round began to unravel with bogeys at the par-four 13th and par-four 16th before the 32-year-old suffered a double-bogey at par-three 18th when her tee shot found the water.
Lincicome immediately steadied the ship with a pair of pars before rolling in a 30-foot birdie putt at the par-four third that brought her to three-over for the day.
But her good work was undone with an ugly triple-bogey on the par-three seventh where her tee shot landed well right of the green and left her with a challenging pitch.
"Literally two bad holes and if I can do better on those two holes tomorrow we'll be pretty good," said Lincicome.
Merritt, whose lone PGA Tour win came at the 2015 Quicken Loans National, equalled the course record with an opening 62 that included an eagle and two birdies over his final four holes.
He nearly set a new course mark but his 11-foot putt at his final hole was about three inches short.
(Reporting by Frank Pingue in Toronto; Additional reporting by Steve Keating; Editing by Peter Rutherford)
