In April 2018, Nauert voiced support for Saudi Arabian-led intervention in Yemen. She also condemned "Iran's malign influence" in Yemen. In May 2018, Nauert said in response to the Gaza border protests: "We oppose actions against Israel at the International Criminal Court (...) because it does not help the cause for peace."
In August 2018, Canada called for the immediate release of Saudi human rights activist Raif Badawi and his sister, Samar Badawi. In response to Canada's criticism, Saudi Arabia expelled the Ambassador of Canada and froze trade with Canada, leading to a decline in Canada–Saudi Arabia relations. Nauert said: "It is up for the Government of Saudi Arabia and the Canadians to work this out. Both sides need to diplomatically resolve this together. We cannot do it for them."
On December 6, 2018, major news organizations reported that Trump had picked Nauert to become United States Ambassador to the United Nations. On December 7 he announced that he would nominate her to the position. Trump told reporters that Nauert was "excellent," adding, "She’s been a supporter for a long time." Upon the announcement of her selection, news outlets noted that she had risen rapidly through the ranks of the State Department and that she had little official foreign policy experience (though in her time as a reporter she had interviewed numerous foreign officials and world leaders). Politico wrote, "Less than two years ago, Heather Nauert was conducting interviews on 'Fox and Friends.' Now, she’s preparing to navigate the world’s raging geopolitical issues." A Washington Post headline read, "Heather Nauert once cited D-Day in 'long history' of U.S.-German relations. Now she’s headed to the U.N."