The 27-year-old back-row forward is set to arrive at Scotstoun this summer once the Pumas conclude their 2026 Currie Cup season. He becomes the first new addition ahead of the upcoming campaign under head coach Franco Smith.
Van der Merwe developed through the University of the Free State system and earned his first professional contract with the Pumas in 2022, following impressive performances in the Varsity Cup.
In 2023, he played a key role in the Pumas squad that reached the Currie Cup final, ultimately finishing as runners-up to the Toyota Cheetahs.
He later captained the side to victory in the 2025 SA Cup, leading them through an unbeaten 11-game run that ended with a 39-14 triumph over the Griquas in the final.
Speaking after the move was announced, van der Merwe shared his enthusiasm about joining the club: "I'm incredibly excited and very grateful to have signed with Glasgow Warriors.
"I've followed the club for a while, and I never imagined I'd get the opportunity to be part of such a prestigious setup. I'm looking forward to giving my best and contributing wherever I can.
"I spoke to Franco before signing, who told me a lot about the environment and his coaching approach. What stood out is how much he values the individual and focuses on developing areas of your game that need improvement.
"I also spoke to Henco Venter, who had nothing but great things to say about the club and life in Glasgow, which made the decision even more exciting for me and my family.
"Supporters can expect a physical edge from me. Coming from South Africa, that's something I take pride in. I enjoy carrying hard, using a mix of strength and speed, getting my hands free for offloads, and contributing physically on defence and at set-piece time. I want to make an impact in all areas and add as much as I can to the team."
Head coach Smith also welcomed the signing, highlighting the qualities van der Merwe brings: "Ruwald is a player that we have been keeping an eye on for a while, having identified him as someone that we believe can bring real value to what we are aiming to build here.
"He is a strong carrier who brings a real work ethic to everything he does, and he is excited to become a Glasgow Warrior from next season."
"We know that the Warrior Nation will welcome him with open arms, and we look forward to welcoming him to Scotstoun later this year."