The new SuperSport shot-stopper joins a long list of Pirates academy products who have left Bucs for other PSL clubs in recent times.
Mkhize's business manager Lizwe Mthethwa of Aftersec Sport Group confirmed the move when speaking exclusively to Goal.
"Sibongiseni Mkhize has signed with SuperSport United. And yes it's a great move for the kid. We need him to get back into the national team," Mthethwa told Goal.
'Bhodwe' was part of the Amajita squad that won the 2013 Cosafa Under-20 tournament in Lesotho, even though he didn't register a single appearance.
"SuperSport offered him a three-year deal, and Sibongiseni signed it. He belongs to the Matsatsantsa," he said.
Immediately after inking the three-year deal with SuperSport, the 18-year-old was then loaned out to National First Division (NFD) side FC Cape Town.
"Mkhize is going out on loan to FC Cape Town for a season-long loan. Cape Town's first choice goalkeeper is struggling with a knee injury. So they needed another keeper," he concluded.