Just hours out from Australia's crunch clash with Sri Lanka, selectors confirmed that Smith would now be part of the group after initially being overlooked.
The batting maestro was flown to Sri Lanka last week after captain Mitch Marsh suffered a testicular injury when struck in the nets before Australia's first game.
Australia are confident Marsh is on the mend from that injury and that Marcus Stoinis will also overcome a hand injury in time to face Sri Lanka on Monday night.
But with their tournament on the line selectors have still issued an SOS to Smith, given a loss could dump them out of the tournament if Zimbabwe beat Ireland on Tuesday.
Smith was overlooked from Australia's preliminary World Cup squad in early January, before blitzing the BBL with the Sydney Sixers after the Ashes.
Selectors then resisted the urge to add Smith into the squad when it was finalised at the end of January, drawing criticism from the likes of Mark Waugh.
That spotlight has only intensified following Australia's shock loss to Zimbabwe on Friday night, which left their tournament on the rocks.
Smith has not played a T20 for Australia since February 2024, but has made no secret of his desire to get back into the side and go to the 2028 Olympics.
The 36-year-old trained with Australia in Kandy on Sunday, and was officially activated as a replacement player that night in order to be available for the Sri Lanka clash.
"ICC regulations stipulate any squad change must be submitted and activated at least one day prior to a match," selector Tony Dodemaide said.
"With Steve here, along with some uncertainty around Mitch and Marcus Stoinis, it made sense he (Smith) is activated and available for selection in time for the match, if required."
Smith's call up means Sean Abbott has for now been overlooked as an option to come into the squad for Hazlewood, which would have given Australia a fourth quick.
The former captain is in Sri Lanka and can still theoretically be added later, if Marsh, Stoinis or any other player is ruled out of the tournament.
Stoinis had said on Sunday night that he was confident he could be fit to face Sri Lanka, while Marsh also "trained strongly".
"The hand's pretty good," Stoinis said.
"Got the scan and there's no break there or anything like that, so it's just a bit battered and bruised, but much better than I thought, to be honest."
Even if Australia beat Sri Lanka, there is every chance they could still need to rely on net run rate in order to progress out of the group.
If Australia do not progress from the group stage, it would mark the team's worst result at a T20 World Cup since 2009.
"Obviously, the boys are pretty disappointed with the result, but we've got no-one to blame but ourselves, and Zimbabwe played really well," Stoinis said.
22°C