Van der Merwe had signed a short-term contract with
Saracens F.C. following a break-out performance for Canada at the
2007 Rugby World Cup. Van der Merwe had appeared for the team in a number of A League matches as well as making appearances in the
2007–08 EDF Energy Cup. However, Van der Merwe suffered a serious ankle injury which sidelined him for 18 months. This injury saw Van der Merwe miss the
2008 Churchill Cup and Canada's 2008 European tour as well as ending his time with Saracens. Following the
2009 Churchill Cup, Van der Merwe joined
Glasgow Warriors on a two-year contract. Van der Merwe debuted for the Scottish side as a replacement against the
Cardiff Blues in October of that year. During the
2009–10 Celtic League season van der Merwe made 11 appearances scoring 4 tries in the process for a total of 20 points as well as playing in 4 matches of the
2009–10 Heineken Cup. The
2010–11 Celtic League season saw Van der Merwe come into his own, starting 19 matches and picking up nine tries along the way. Van der Merwe finished as Glasgow's highest try scorer for the season as well as finishing tied for third with
Jonathan Davies in the Celtic League's leading try-scorer category. Van der Merwe also started 5 matches and score 3 more tries in the
2010–11 Heineken Cup. In March 2011, Van der Merwe re-signed with Glasgow Warriors on a two-year deal. Following the conclusion of the 2011 Rugby World Cup it was discovered that Van der Merwe sustained some damage while playing in the tournament and was serious enough to require shoulder surgery. Van der Merwe was expected to miss most if not all of the
2011–12 Celtic League season though he returned to the Glasgow line up on the bench for the important RaboDirect Pro12 match against Treviso in Italy towards the end of the regular 2011/12 season. He was brought on as a substitute as the game looked to be slipping away from the Warriors when he picked up a ball in the midfield in the 76th Minute and scored a deciding try. On 19 February 2015, it was confirmed that Van der Merwe had signed a contract with the
Scarlets, leaving
Glasgow Warriors after the 2014/15 season. He currently has 39 tries in 90 appearances for the Scottish club. His final game for the club was their victory in the 2014/15 Pro 12 final, in which Van der Merwe scored a try. Van der Merwe missed the first few games of his debut Scarlets season due to being with Canada at the
Rugby World Cup. But once he returned, he made quite an impact, scoring two tries on his debut in a 25–14 victory against
Leinster. On 4 January 2017, it was announced Van der Merwe was leaving the Scarlets at the end of the 2016–17 season. It was announced on 22 February that Merwe has signed for English club
Newcastle Falcons in the
Aviva Premiership from the 2017–18 season. However, on 15 March 2018, Van der Merwe left Newcastle with immediate effect to re-sign for
Glasgow Warriors back in the
Pro14. Van der Merwe was drafted to
Ayr in the
Scottish Premiership for the 2018–19 season. He left Glasgow Warriors as their then all-time leading try scorer with 54 tries, but his record was later beaten by
George Horne. Van der Merwe joined the
LA Giltinis ahead of the
2021 Major League Rugby season, spending two seasons with the club. Van der Merwe retired from rugby after the Giltinis were expelled from the MLR ahead of the 2022 playoffs due to a violation of league rules and the club was disbanded. ==International career==