Sangweni, who was recently training with champions Bidvest Wits, has penned a contract at Mayfair that will run until 2020.
He told Bucs' website: “I am very happy to have joined the club. I look forward to making a positive contribution to the team and help the team to bounce back to where we all know it belongs.
“I would like to thank from the chairman, to the staff and the supporters of Chippa United for all they have done for me, I will be forever grateful.”
The 28-year-old's older brother Siyabonga Sangweni starred at Pirates before a knee injury forced him to retire in April 2016.