Powell’s knock came off only 18 balls as the West Indies reached their target of 132 with three balls to spare to go 1-0 up in the three-match series.
The game was reduced to 11 overs each with South Africa scoring 131-8 and then the tourists replying with 132-7.
After a two-hour delay, Powell put South Africa into bat in damp conditions and got immediate returns as key batsmen Quinton de Kock and Rilee Rossouw departed cheaply.
David Miller came to the home side’s rescue by scoring 48 off 22 balls, which coupled with cameos from Reeza Hendricks (21) and Sisanda Magala (18 not out), took South Africa to a defendable total.
West Indies went on the attack from the start of their innings, scoring 17 runs off their opening four balls before South Africa snagged Kyle Mayers with the next delivery.
Brandon King (23) and Johnson Charles (28) continued to bully the bowlers before Powell hit three sixes and a four as the West Indies plundered 25 runs off Bjorn Fortuin in the eighth over.
It left them needing 20 runs off the last three overs but what should have been a routine assignment was frustrated by two wickets in as many balls for Magala before Powell ensured victory in the last over.
The second T20 clash will also be contested at Centurion on Sunday.
