Melville's first Foreign Service assignment was in the U.S. Embassy to the German Democratic Republic from 1986 to 1988.

In Washington, he worked in Legislative Affairs, as a Senior Watch Officer in the Operations Center, and at the Foreign Service Board of Examiners.

Melville's most recent position with the State Department was as the Deputy Chief of Mission in the U.S. Embassy Berlin, Germany.

He presented his credentials to President Toomas Hendrik Ilves on December 8, 2015.

[2] On June 29, 2018, he resigned as Ambassador over President Donald Trump’s statements in regards to NATO and the European Union,[4][5][6] effective on July 29, 2018.