Handscomb struck 103no off 64 balls, reaching his first Big Bash League ton with a six that finished the match as the Stars successfully overhauled the Scorchers??? 179-2 with three balls to spare despite a first-ball duck for Kevin Pietersen.
The win wasn???t good enough to lift the third-placed Stars above the Scorchers, who remain second and favourites to host the second semi-final by virtue of a superior run-rate but it was a timely victory should the two teams meet again in the last-four of the competition.
Handscomb, making only his second BBL appearance of the competition due to injury, walked to the crease with the Stars 8-2 after Pietersen had been bowled first ball by Yasir Arafat (4-27) following Luke Wright???s cheap dismissal, caught at mid-off for one.
The 23-year-old reached his maiden BBL fifty off 45 balls with a slog-swept six off spinner Ashton Agar but despite his efforts the Stars still required an unlikely 66 runs from the final 30 balls with five wickets in the bank.
But together with John Hastings, who smashed Agar for three sixes in a row, the pair turned the tide in the final overs of the innings.
Hastings helped himself to 20 off six balls before launching Agar high into the sky, wicketkeeper Sam Whiteman running towards mid-off to take the catch.
His innings left the Stars needing 30 off 18 balls and then 12 off the final over, Handscomb making light work of the task by hitting the first and third balls of Andrew Tye???s over for six.
Perth had earlier cashed in after winning the toss as Shaun Marsh and Michael Klinger put on 127 for the first wicket off 14 overs to pave the way for a challenging total.
Marsh struck three sixes and eight fours to plunder 79 off just 51 balls before holing out in the deep off the bowling of Michael Beer.
Klinger???s knock was almost as explosive, his 71 off 48 balls featuring two maximums, and helped to add 52 off the final six overs with skipper Adam Voges (27no off 21 balls).
The opener was run out off the final delivery of the innings, failing to make his ground at the non-striker???s end, beaten by Jackson Bird???s accurate throw.
Reflecting on the Stars??? victory, former England all-rounder Dominic Cork said: ???This game keeps surprising me. Who???d have thought that would have happened?
???Handscomb probably shouldn???t be playing if you think of guys like Mike Hussey and Glenn Maxwell, who weren???t involved but what an innings. Some of the shots were fantastic.
???It???s great to see ??? Twenty20 is alive. He enjoyed it, his team enjoyed it; we thought it was going to be a Pietersen show and it wasn???t.???