On 16 December 2015, he was appointed minister of climate and the environment, a position he held until early 2018, when he was succeeded by Ola Elvestuen once the Liberal Party had entered government.

He became the first minister of European affairs on 16 October 2013, a newly created ministerial post in Solberg's Cabinet following the Conservative victory in the 2013 election.

[6] In late April 2015, Helgesen expressed concerns about Hungarian prime minister Viktor Orbán's comments that the death penalty should be a relevant debate.

[8] Helgesen was among the guests invited to the state dinner hosted by U.S. President Barack Obama in May 2016, which was in honor of Solberg and other Nordic leaders Lars Løkke Rasmussen, Sauli Niinistö, Sigurður Ingi Jóhannsson and Stefan Löfven at the White House.

[10] In November 2023, it was announced that Helgesen would be appointed Executive Secretary of the Intergovernmental Oceanographic Commission, with the rank of Assistant Director-General at UNESCO.