Klemm joined the
United States Foreign Service in 1981 and was promoted into the
Senior Foreign Service in 2001. From 2012 to 2015 he was Principal Deputy Assistant Secretary in the State Department's Bureau of Human Resources. As of January 2015, Klemm served as Senior Advisor to the
Under Secretary for Management at the Department of State. In March 2015 President Barack Obama announced his intent to nominate Klemm as
U.S. Ambassador to Romania. In September 2015, Klemm assumed the duties of U.S. Ambassador to Romania. In 2016, Hans G. Klemm, together with other local officials, were pictured with a
Székely flag during his visit to the
Székely Land. The photo was posted by the mayor of
Sfântu Gheorghe on Facebook. The reactions of the politicians in Bucharest were turbulent. In a response Klemm affirmed that the only two flags that are important to him, as a diplomat, are the U.S. and the Romanian ones. ==Honour==