Following his graduation in 2009, Hauptmann started working as head of office and parliamentary assistant to Christian Hirte, MP (CDU) at the German Bundestag in Berlin.

Hauptmann worked at the European Parliament in Brussels, Belgium, for the Konrad Adenauer Foundation's office in Beijing, China, as well as the Thuringia's State Ministry of Transportation, Construction and Economic Development.

Since then, he became a member of the federal board of the Young Union and was appointed chairman of JU's International Commission on Foreign, European and Security Affairs until 2014.

[4][5] In March 2021, magazine Der Spiegel reported that the Azerbaijani embassy in Berlin paid €16,744 to advertise a shopping weekend in Baku in a local newspaper that Hauptmann publishes in the state of Thuringia.

According to the report, the payment was made after Hauptmann had worked for years to establish cordial ties with Azerbaijan, consistently siding with the country despite its controversial human rights record.

[10] In 2019, Hauptmann joined fellow CDU lawmakers – including Roderich Kiesewetter and Norbert Röttgen – in co-signing an op-ed in Handelsblatt, calling on Chancellor Angela Merkel to keep Chinese telecom company Huawei out of Germany's 5G network, citing national security reasons.