Although born in Vanderbijlpark, Van der Merwe grew up in George, where he played rugby for Outeniqua High School to win inclusion in the Under-16 side for the 2007 Grant Khomo Week and their Under-18 side for the 2008 Academy Week and 2009 Craven Week competitions. In 2010, he moved to Potchefstroom where he represented the and university side. He was a regular for the side during the 2010 Under-19 Provincial Championship competition, making thirteen appearances and in 2012, he made twelve appearances for the side in the 2012 Under-21 Provincial Championship, scoring six tries. He played Varsity Cup rugby for the in 2013 and 2014. He made eight appearances and scored three tries in the 2014 competition, helping his side to the final, where they lost 39–33 to the, with Van der Merwe scoring a try early in the second half.
Leopards
His senior debut came in 2013, when he was included in the senior side for the 2013 Vodacom Cup competition. He made his debut against the in Johannesburg, coming on as an early substitute. He also marked the occasion by scoring a try in injury time at the end of the match. Two more starts and three more substitute appearances followed during that competition. His Currie Cup debut came in July 2013. He came on as a substitute on the hour mark at Olën Park in their 2013 Currie Cup First Division match against the eventual champions, the. While mainly being used as a substitute during the campaign, he did one start in the competition against the. He made a further two appearances for the Leopards during the 2014 Currie Cup qualification tournament.
Lions
In April 2014, Van der Merwe was a surprise inclusion in the touring squad for their Australian leg of the 2014 Super Rugby season. He made his Super Rugby debut against the in Hamilton and scored his first try for the Lions in their next match against the in Dunedin. After one more match that he played off the bench, he made his first Super Rugby start in their final tour match against the in Perth. On 4 April 2015, he scored a last-minute winning in their 2015 Super Rugby season match against the to help the Lions win the match 22–18 against their trans-Jukskei rivals.
Golden Lions
His performances for the in Super Rugby also led to a domestic move, with Van der Merwe joining the on a deal for the 2014 Currie Cup Premier Division competition.
He is the older brother of wingerDuhan van der Merwe, who also played Craven Week rugby for and were included in the South African Schools sides in 2012 and 2013.
