The younger brother of former Southern Kings Lock/Back Row Stefan Willemse, Jaco attended a source of countless Springboks, Paarl Gymnasium. Having represented Western Province since the age of 16, his form at the U18 Craven Week of 2014 was rewarded with South Africa U18 selection. His imposing style of play soon brought comparisons with both his namesake Paul Willemse and Bakkies Botha, as Jaco continued to physically dominate opponents in both the U19 and U21 Currie Cup competitions.

One of the most promising players in the country, the Golden Lions aggressively recruited Willemse and the excellent ball carrier made Johannesburg home before the 2017 season. Crossing the advantage line with ease and showing handling of a modern tight forward, his senior professional debut for the Lions was unfortunately followed by an injury that saw him sit out much of the 2018/19 season. Returning to his best in time for 2019/20, Jaco was signed by Fédérale 1’s ambitious Lannemezan. Perfectly suited to the confrontation of the French game, Jaco Willemse is expected to quickly progress up the ranks.