Following law studies and legal clerkship in Cologne, Berndt Hess was admitted to the bar in 1994. He gained his first professional experience in a law firm in Cologne, advising clients mainly on matters of civil law.

In 1996, Berndt Hess joined the Frankfurt office of Clifford Chance as an associate lawyer, becoming a partner in 2000. His practice focused on German and EU antitrust law and on compliance matters.

Between 2014 and 2017, Berndt Hess was head of antitrust compliance and compliance officer in charge of several divisions at Bilfinger SE. During this period, the company was under the supervision of a compliance monitor appointed by the US Department of Justice.

In May 2017, Berndt Hess established his own independent practice.