Czech star Pliskova stormed past second seed Halep 7-5 6-1 in a rain-interrupted semi-final clash at the Premier Mandatory event.
Halep led 5-3 in the opening set, however, Pliskova reeled off the next four games to stun the world number one hopeful.
Pliskova won 10 of the last 11 games against Halep – who needed to reach the Miami final to dislodge Naomi Osaka atop the WTA rankings – hitting 23 winners and 16 unforced errors.
There was another rain delay as Pliskova moved within a game of a showdown with Ashleigh Barty – play eventually resuming after 01:00 local time (05:00 GMT).
Halep returned and managed to avoid a second-set bagel but it only temporarily halted the inevitable in the early hours of Friday morning.
"Not easy, day and night, because we waited for so long," Pliskova – who converted five of seven break-point chances – said. "The conditions can change here in Miami so I think we were both ready for this day because since the morning it was tough.
"But I stayed half the day in the hotel which was nice and now it was a little bit long, but after the first break I just started playing a little bit better. I was fighting a bit more and just playing more aggressive and it paid off."