Olivier Riesen studied law and economics at the University of Geneva. After his studies, he commenced his legal career as a trainee notary in Nyon. Following this initial experience, Olivier joined a law firm in Geneva, known today under the name of Pestalozzi Attorneys at Law, where he completed his legal training.

After successfully completing his bar exam in 2001, Olivier worked for the Swiss Competition Commission in Bern, where he was team manager in charge of the automotive industry, consumer goods and construction. During this time, Olivier was seconded for several months, as a Swiss national expert, to the Director-General for Competition of the European Commission in Brussels.

With the benefit of this experience, Olivier returned to the private sector and joined Lenz & Staehelin where he was active in the departments of competition and real estate law, both in Geneva and Zurich.

In 2009, Olivier became an independent lawyer joining a boutique law firm as partner in Geneva.

In 2012, Olivier established his own law firm in Nyon. He regularly speaks at conferences and has published a number of articles in English and German on competition law. He practices in French, English, German and Swiss German.