A product of the University of the Free State, van der Merwe first signed professional terms with the Pumas in 2022 after impressing in the Varsity Cup.
A year later the back-rower was part of the Pumas squad that enjoyed a standout run to the Currie Cup final, with only the Toyota Cheetahs denying van der Merwe and his team-mates the title.
Van der Merwe captained the Pumas to glory in the 2025 SA Cup, leading his squad to the title with an 11-match winning streak that culminated in a 39-14 win over the Griquas in the Grand Final.