He has also served as director general of the International Union for Conservation of Nature (IUCN) and secretary-general of the World Commission on Dams.

At the time, he was not nominated by a Member State, but prevailed over candidates such as Børge Brende of Norway and Rajendra K. Pachauri of India.

[6] In addition to his role at the University of Oxford, Steiner was appointed Envoy of the Chair of the Platform on Disaster Displacement by the Federal Government of Germany in October 2016.

[7] In late 2015, Reuters reported that Steiner was one of three candidates shortlisted to succeed António Guterres as United Nations High Commissioner for Refugees, alongside Helle Thorning-Schmidt of Denmark, Jasmine Whitbread of the United Kingdom, and Filippo Grandi of Italy;[8][9] the post eventually went to Grandi.

In November 2018, Guterres also appointed Steiner to co-chair (alongside Maria Ramos) the United Nations Task Force on Digital Financing of Sustainable Development Goals.