The 24-year-old has put pen to paper on a two-year deal at Scotstoun and will join up with Gregor Townsend’s squad for pre-season training at the end of the month.
The 6ft 1in tighthead began his senior career in Pretoria, making his debut for the Blue Bulls in 2009. He went on to make 41 appearances for the club, 14 of which were in Super Rugby.
In 2013, De Klerk joined the Cheetahs, where he featured in the Vodacom Cup and Currie Cup and he played seven times in Super Rugby for them this season.
He said: “I’m delighted to have signed for the Warriors and I’m looking forward to playing in the Guninness Pro12 and European Rugby Champions Cup next season. It’s always been an ambition of mine to play for a European club and I’m looking forward to going over to Scotland later this month and meeting my new team-mates in Glasgow.
“I’m expecting tough competition to get into the team but that is a great challenge and something which really motivates me.
“Glasgow have made excellent progress over the last couple of seasons and I’m looking forward to being a part of that.”
De Klerk is the third prop to join Glasgow this summer and fifth signing ahead of the new season, following the arrivals of Alex Allan, Euan Murray, James Downey and Murray McConnell.
Townsend added: “To get a tighthead of Rossouw’s quality into the club is fantastic and he’ll add depth and competition to our front-row.
“Playing in that position, you know you’re going to play a lot of rugby throughout the season and Rossouw already has a lot of experience for a 24-year-old. Rossouw is very good in the loose and a strong tackler.
“It’s great news that he’s joining us and we look forward to welcoming him to the club later this month.”