In 1989 he received his PhD in Philosophy from the University of Tübingen with a thesis on social contract theories.

As a recipient of an Alexander-von-Humboldt Fellowship, he spent 1993/94 at the Faculty of Law and the Department of Philosophy of the University of Toronto.

Bielefeldt teaches in the areas of political science, philosophy, law and history.

Between 18 June 2010 and 31 October 2016 Bielefeldt was the appointed United Nations Special Rapporteur on Freedom of Religion or Belief by UN Secretary General Ban Ki-moon.

In 2018 Bielefeldt and his co-authors, Nazila Ghanea and Michael Wiener, where given the inaugural (Senior) Alberigo Award for their 2016 work,Freedom of Religion or Belief: An International Law Commentary.