Thanks to Erin Burns, who opened the batting and carried her bat with 60 not out from 45 deliveries, and Ashleigh Gardner (54 from 42), the Sixers posted a sizeable 6/164 which the Scorchers chased down with four balls to spare. It was Burns highest WBBL score for the Sixers.
The home side finished 2/165. Australian and Perth captain Meg Lanning top-scoring for the Scorchers with 81 from 50 deliveries including nine fours and two sixes.
A 104-run opening partnership with England International Amy Jones (41 from 42) was key to victory.
The contest was a lot closer than Saturday, at the same venue, when the Scorchers prevailed by 52 runs. The Sixers hang onto fourth position, on the WBBL table, despite the loss but have two big games against the Adelaide Strikers next weekend to ensure qualification for the finals.
A brilliant running catch on the boundary by recent Sixers recruit Hollie Armitage eventually dismissed Lanning and was one of two outstanding catches for the English woman.
She also removed Jones with a magnificent forward diving effort, full stretch, centimetres from the ground at mid-off, her first in the WBBL.
The fifties for Burns and Gardner were their first of WBBL|05. The pair shared a second wicket stand of 82 after stand-in captain Alyssa Healy departed first ball of the match to English seam bowling allrounder Nat Sciver (1-35), caught and bowled.
Sciver also made a quick fire 39 not out from 22 and hit the winning runs with consecutive boundaries in the final over.
Burns hit seven fours and brought up her fifty with a six down the ground, while Gardner looked in ominous form before departing, striking eight fours and two sixes.
Seamer Sam Betts (2-20) returned best figures for Perth. For the Sixers, Gardner picked up both wickets with her off-spin.