Dimitrov was on court for nearly two-and-a-half hours before finally subduing the British number two, who was right in the contest until he hurt his ankle with the score at 4-4 in the third set.
"I thought I was out - he pushed me to the limit, " Dimitrov said.
Edmund had to save two break points in the ninth game of the second set and, encouraged, he swept through the tie-break to deservedly level the match.
Although Edmund recovered to continue playing, he couldn't win a game from thereon as Dimitrov went on to clinch a 6-3 6-7 6-4 win and set up a semi-final date with local hope Nick Kyrgios. "It's very unfortunate what happened, for sure". That's just me, I guess.
"First match in about a month - I feel a little bit rusty, but at the same time I'm excited and trying to get into a rhythm".
"I only know kind of the initial feelings of it, which is not always so trustworthy, " she said of the injury.
But Millman, the fourth-ranked Australian, was prepared a few hours later to play Sydney qualifying, starting Saturday afternoon, but should have earnt himself the third and last of Tennis Australia's wildcards for the tournament's main draw. It's just tough when you come up against the top seed (Dimitrov) and I would love to win one of those really big ones.
The other final four clash sees Ryan Harrison face teenager Alex De Minaur.
Harrison moved through when his opponent, Uzbekistan's Denis Istomin, retired due to a left hip injury with the American leading 7-6 (8/6), 4-2.