In 2012, Louw got his first provincial representation when he was called up by Boland to represent them at the 2012 Craven Week competition in Port Elizabeth. Shortly after the competition, Louw was also named in the 2012 South African Schools squad. He played in three matches for them – against France, Wales and England, helping South Africa to victories in all those matches. After finishing school, Louw moved to Pretoria for the 2013 season to join the. He made twelve appearances for the side during the 2013 Under-19 Provincial Championship, helping them win twelve matches in a row in the pool stages. He scored a try in their semi-final match with to help the Blue Bulls reach the final with a 37–21 victory. He played off the bench in the final against the s, a match which the BlueBulls won 35–23 to secure the championship. In 2014, Louw was included in the South Africa Under-20 squad that participated in the 2014 IRB Junior World Championship held in New Zealand. He started their opening match against Scotland before playing off the bench in a 33–24 victory against hosts and four-time winners New Zealand. He once again started their final pool match, a 21–8 victory over Samoa as South Africa finished top of the group to set up a rematch with New Zealand in the semi-finals. Louw came on as a replacement in their semi-final to help South Africa secure their fourth consecutive victory over New Zealand at this level, winning 32–25. He made his fifth appearance of the tournament in the final, but could not prevent South Africa finishing on the losing side this time, with England winning the championship for the second consecutive year with a 21–20 victory over South Africa. Louw returned to domestic action after the Junior World Championship, making five starts for the s during the 2014 Under-21 Provincial Championship and scoring a try against the team as they reached the final of the competition and eventually winning the title by beating in the final.
In October 2014, it was announced that Louw would return to the Western Cape by joining ahead of the 2015 season. He was named in the wider training group of their Super Rugby side the, and then included in their final squad for the season. He was then named on the bench for their season-opening match against the.
Louw was called up to the Springboks for the 2017 Rugby Championship following Coenie Oosthuizen's broken arm. Louw made his debut for the Springboks off the bench in the final round of the tournament which was a 24–25 loss to New Zealand.
