The defender arrives in Port Elizabeth with a wealth of experience, having been part of the Mamelodi Sundowns team which won the CAF Champions League in 2016.
Chippa executive chairman Siviwe Mpengesi confirmed the signing of Nthethe, who joins the Chilli Boys as a free agent after his deal with PSL champions Sundowns was not renewed.
"Thabo is a player with the right characteristics and a perfect fit for the club," Mpengesi told his club's official website.
"He is a defender that is comfortable with the ball. He is a leader on and off the pitch. We are delighted to have him on board.
"We have a relatively young team and we have no doubt that Thabo will share his experience positively with the rest of the squad.
"We welcome him to the Eastern Cape and wish him all the best."