The 27-year-old, who is equally as adept at left-back as left wing, opted to return home after almost eight years in the States.
New England Revolution were keen on the player's services, with his contract in Toronto having recently expired .
He was selected by the Massachusetts-based side at stage 1 of the draft in December 2011 - but has since successfully completed a trial with United.
Following spells with Rhode Island Stingrays and New York Red Bulls, Borman joined Toronto. He has also represented the South Africa U20 side.
He told the Sowetan: "I'm very happy to join SuperSport.
"From what I have heard, they are a go-ahead club and I will be eager to make my mark in the PSL."
Borman is joined at United by another Capetonian, Mark McCarthy, younger brother of Jerome and Benni.