He was the political advisor to the United Nations Assistance Mission for Iraq (UNAMI) in 2003, where he played a critical role in bringing together Iraqi factions.

On 22 June 2017, Salamé was appointed Head of the United Nations Support Mission in Libya (UNSMIL), replacing Martin Kobler.

[14] In February 2020, he eventually brought delegations from the two main sides in Libya's conflict to Geneva for peace talks, but key representatives suspended their involvement.

[15] On 2 March 2020, Salamé resigned as the head of the United Nations Support Mission in Libya citing stress and health concerns.

In a statement on Twitter, he said he had been frustrated with foreign powers, particularly France and Russia for covertly backing Khalifa Haftar's forces in the civil war.