In 2013, he played Varsity Cup rugby with the UCT Ikey Tigers, scoring three tries in six starts.
He made his Currie Cup debut a few months later when he came off the substitutes' bench for their match against Sharks following Tiaan Liebenberg's late withdrawal through injury.
[3][4] In 2014, he was called up into the Stormers squad for their 2014 Super Rugby match against the Sharks, following Deon Fourie's late withdrawal through injury.
[5] On 25 March 2019, Willemse would travel to Scotland to sign for Edinburgh in the Pro14 on a two-year deal from the 2019-20 season.
[6] Following his release from Edinburgh, he signed for English club London Irish in the Premiership Rugby from the 2021-22 season.