Willem Mathlener started his musical studies in Pretoria, South Africa, where he received violin lessons from Hester Woliz-Udal, Annemarie Swanepoel and Denise Sutton. During that time he was a member of the Chamber Orchestra of South Africa, Johannesburg Philharmonic Orchestra as well as free lance musician for most of the professional orchestras in South Africa.
In 2005 he was awarded the Associated Board International Scholarship to further his studies at the Royal Scottish Academy of Music and Drama studying under Peter Lissauer and viola under Catherine Marwood. During this time he won several competitions, including 20th century chamber music for violin and piano and viola challenge prizes.