The Gippsland golfer was the big improver on a day when the moves came thick and fast as overnight leaders Daniel Popovic and China's Zhang Xin Jun stared each other down over the front nine before making the turn tied on 11-under.
Brown was three under par and seven off the pace heading into Saturday's third round.
He weaved his way through the field from 28th position to have a share of the lead when he holed a short birdie putt to end his spectacular round.
After opening with a birdie at the first hole he collected further birdies at the fifth, sixth, seventh and ninth holes to go out in 31 shots.
Four more birdies and a solitary bogey, at the par-4 356 metre 13th hole, completed his charge.
"I had a couple of slightly jittery holes towards the end of the back nine so it was nice to hit a good drive down 18 and then hit an iron nice and close. I'm very happy," he said.
"It hasn't been the best year for me but I've been playing better the last few months although I didn't really have any expectations at the start of the day.
"But whenever you shoot 64 in any tournament, let alone the Aussie PGA you take it."
Brown said his birdie at the fifth hole out of the trees had been the turning point in his round.
"I hit an ordinary second shot into the trees but got a good break away from the signage and holed a 25 foot putt for birdie and then birdied the next two holes. That was the turning point.
"There are a lot of birdies out there but it is the kind of course where things can go pear shaped very quickly too."
Co-overnight leader Popovic was 11-under with three holes to play while last weekend's Australian Open winner Peter Senior was looming large on nine-under with two holes to play.
-12: Daniel Popovic (AUS) 17 holes
-11: Anthony Brown (AUS) 18 holes
-10: Peter Senior (AUS) 18 holes, Matthew Griffin (AUS) 17 holes
-9: Brendan Jones (AUS) 18 holes, Mathew Goggin (AUS) 18 holes, Brad Kennedy (AUS) 18 holes, Rod Pampling (AUS) 18 holes
-8: Geoff Ogilvy (AUS) 17 holes, Robert Allenby (AUS) 18 holes, Stephen Dartnall (AUS) 18 holes