Koen Rens started violin lessons as a Suzuki student with Jeanne Janssens in Turnhout, Belgium. Later on, as a student of Dirk Lippens, he won the degree of excellence in the Conservatorium of Bruges, where he made his debut as a soloist with orchestra. He then studied at the Royal Conservatory of Music in Brussels and won first prizes in violin and chamber music in 1989, studying with Katalyn Sébèstyen and Guido De Neve. He obtained the final diploma of the European Suzuki Association in Suzuki pedagogy in 1992.

He played with the chamber orchestra of the European Community, the Sallinen String Quartet and the Rubens Piano Trio, and with the folk band Galley Head. He was appointed as a Teacher Trainer for ESA in 2000.

In 2002 he went to study violin, psychology and pedagogy in the Conservatoire Royal de Liège and got the final diploma in 2003 with a thesis on the development of autonomy in Suzuki-trained students.

Koen Rens has a thriving studio for almost 30 years now and is teaching violin and conducting the Symphony Orchestra at the Academy of Music in Turnhout, Belgium. He has been invited to teach and perform in most European countries, South Africa, Mexico, Canada, United States, Japan, Taiwan and Australia.

In 2009 he was appointed Chairman of the European Suzuki Association and worked as such towards a more active role of the Suzuki Philosophy in the everyday workings of the European Suzuki Community. Together with Wilfried Van Gorp he founded and directs the Belgian Suzuki Chamber Orchestra.

Since 2005 he is director of the Suzuki violin Teacher training program for the Lithuanian Suzuki Association and since 2014 for the LSA in Latvia. Since 2015 he also trains teachers for the Catalunian Suzuki Association in Barcelona (Spain). He serves on the Faculty of the AP Royal Conservatory of music in Antwerpen teaching a Postgraduate Course in Suzuki Pedagogy.