Marius van der Westhuizen started refereeing in 2007 in the Western Province Union. He was appointed to the South Africa National Panel in 2011 and Elite Panel in 2013. The Cape Town-based referee had a career-defining year in 2013 when he was called up to officiate two IRB Sevens Finals, the Varsity Cup Final and Vodacom Cup Final. He made his Super Rugby debut in 2014 and has been achieved significant growth in Super Rugby having refereed a Quarter Final in 2017 and he has now taken charge of 44 matches including seven last season. He has also now refereed 11 international matches.