After a slow start Thursday at Spyglass Hill - he was 2 over par through 11 holes - Mickelson has played his last 25 holes in 11 under par.
Americans Kevin Streelman and Beau Hossler posted seven under rounds of 65 to sit in the club house first round lead.
Aged 30, the Australian said he may need to capitalise on that good form as he seeks to add to his lone major title, the 2015 PGA Championship. I'm just trying to get back and I got a little on top of it and I was kind of hitting the ball into the ground with a - with my hands pretty far forward, which is a very, it's opposite of what my natural tendency has been going back to when I was eight years old.
Johnson said he's approaching the form that saw him win three straight tournaments early previous year before he fell on some stairs and hurt his back as he prepared to tee it up in the Masters.
Five-time major-winner Phil Mickelson, a four-time victor in the tournament that teams amateurs from the world of big business, sports and celebrity with the pros, put himself in the mix for the weekend with a bogey-free 65 at Monterey Peninsula that left him tied for fifth on nine-under par.
One former world number one offered rare praise to another on Wednesday as Jason Day said Rory McIlroy had "Tiger-esque" skills on the golf course. "I want to be one of the best players to ever have played the game when I decide to call it a day".
McIlroy had an eagle putt at the hole, but left with a double bogey after an implosion, before two more bogeys followed to finish his round.
The pro-am event sees the professionals and their partners also playing a round at Monterey Peninsula before the final day's action takes place at the famous Pebble Beach public links. Dustin Johnson is just one shot ahead of Lowry, while joining him at four under his fellow countryman and friend, Rory McIlroy.
McIlroy was four-under through 15 holes before suffering a bogey on the 16th, when his wayward drive finished in a waste area.
After two strong performances in the Middle East recently, albeit without a victory, he is eager to make the most of his good health.