Joël de Montmollin studied law at the University of Fribourg. During his studies, he participated in a one-year exchange program with the University of Vienna (Austria). He obtained his Master's degree in 2012 and continued his professional training as a clerk trainee at a District Court, then as a trainee lawyer before obtaining his bar exam in 2016.

After working as a lawyer for a prefecture, he joined EDIFICE Construction & Immobilier Avocats SA (formerly MBP Construction & Immobilier Avocats SA), where he mainly practiced construction and real estate law.