Sale have agreed a deal to sign fly-half Robert du Preez and hooker Akker van der Merwe from Super Rugby side Sharks on three-year contracts.
Du Preez, 25, had a loan spell with the Premiership side earlier this season, scoring 81 points in nine games.
He has won one cap for South Africa and is the brother of fellow Springbok Jean-Luc Du Preez, who has also been on loan at Sale this season.
Van der Merwe, 27, has three caps for the Springboks.
Both players will join the club at the end of the current Super Rugby season.
He began his Super Rugby career in 2014 with the Lions, where he played alongside Sale scrum-half Faf de Klerk, before taking a short-term contract with Racing 92 in France.
Van der Merwe moved to Durban to play for the Sharks in 2017 and helped them win the Currie Cup in the same year, with the Du Preez brothers among his teammates.
"I feel the time is right in my career for a move away from South Africa," van der Merwe told the Sale website.
"I am good mates with Faf De Klerk and having spoken with him, he only has good things to say about Sale so we are really excited about joining the club and experiencing a new lifestyle in Manchester."
Meanwhile, Sale director of rugby Steve Diamond said of du Preez that he was "exactly the calibre of player we are looking for in our bid to challenge for the Premiership".